Why Some Habits Take Far Longer Than Others

Introduction

Some habits take far longer to feel automatic because the behaviour itself is demanding. Drinking a glass of water after breakfast is a short, repeatable action with an obvious cue. Exercising, cooking a healthy meal, completing a study session or following an evening routine may involve preparation, several decisions, changing circumstances and multiple linked actions. Habit research suggests that these differences matter: automaticity can develop over weeks or months, but formation times vary enormously between people and behaviours, and greater behavioural complexity is associated with weaker or less reliable habit development in several studies.[Wiley Online Library]onlinelibrary.wiley.comWiley Online LibraryHow are habits formed: Modelling habit formation in the real world - Lally - 2010 - European Journal of Social Psycho…

This is why there is no scientifically defensible countdown such as “21 days” or even “66 days” that applies to every habit. A 2024 systematic review found individual formation times ranging from 4 to 335 days across the small number of health-habit studies that measured duration directly. More importantly for complex habits, researchers increasingly distinguish between making the start of a behaviour automatic and making an entire multi-step sequence automatic. For self-improvement that lasts, that distinction produces much more realistic expectations.[PubMed Central (PMC)]pmc.ncbi.nlm.nih.govOpen source on nih.gov.

Simple versus complex behaviours

The classic real-world habit-formation study by Phillippa Lally and colleagues illustrates why behaviour type cannot be ignored. Participants chose daily eating, drinking or exercise behaviours and repeated them in a consistent context. Among participants whose automaticity trajectories could be modelled, reaching 95% of their eventual automaticity took between 18 and 254 days. Automaticity rose quickly at first and then more slowly towards a plateau rather than suddenly appearing on a particular day.[Wiley Online Library]onlinelibrary.wiley.comWiley Online LibraryHow are habits formed: Modelling habit formation in the real world - Lally - 2010 - European Journal of Social Psycho…

An important detail is often lost when the study is reduced to its famous 66-day average. Simpler actions, such as drinking water, tended to reach their automaticity plateau more quickly than more elaborate behaviours such as exercise routines. Researchers translating the findings into clinical habit advice subsequently emphasised choosing small, manageable actions partly because simpler actions appeared easier to automate.[PubMed Central (PMC)]pmc.ncbi.nlm.nih.govPubMed Central (PMC)Making health habitual: the psychology of ‘habit-formation’ and general practice - PMCDecember 1, 2012…Published: December 1, 2012

Complexity is not simply a question of how physically difficult something is. A behaviour becomes complex when successful performance depends on coordinating several sub-actions or responding to variable conditions. “Take a vitamin after breakfast” has a fairly consistent structure. “Eat healthily every evening” might require deciding what to cook, checking ingredients, preparing food, resisting convenient alternatives and adapting to changing work or family schedules. “Exercise three evenings a week” may require packing equipment, travelling somewhere, choosing a workout and completing the session.

Research across 25 behaviours, including exercise, handwashing and medication adherence, found that greater perceived behavioural complexity was associated with lower automaticity overall. Frequency, stable contexts and perceived rewards were all positively associated with automaticity. Interestingly, stable context and reward were especially strongly related to automaticity for behaviours perceived as complex, suggesting that complexity does not make habit impossible; it may make reliable cues and favourable conditions more important. Because this study was observational, however, it cannot establish that complexity itself caused slower habit development.[PubMed]pubmed.ncbi.nlm.nih.govHabits, Quick and Easy: Perceived Complexity Moderates the Associations of Contextual Stability and Rewards With Behavioral Automat…

More recent longitudinal evidence strengthens the case that complexity is one source of variation without turning it into a universal law. A preregistered 2026 reanalysis followed 254 people over six months and identified trajectories in which habits either strengthened or degraded. Membership in those trajectories differed according to behavioural complexity, frequency and context stability, while perceived difficulty was negatively associated with habit strength. The study reinforces a broader conclusion: the behaviour being attempted helps shape how smoothly automaticity develops.[Sage Journals]journals.sagepub.comSage JournalsWhat Makes a Habit? Investigating Potential Determinants of Habit Formation - Sebastian Bürgler, Marina Milyavskaya, Gail Mc…

A complex routine may never become automatic in the simple sense

There is a deeper problem with saying that an entire complex behaviour “becomes a habit”. Modern habit theory usually defines a habit as a learned association in which a contextual cue automatically triggers an impulse to act. That definition fits compact behaviours quite neatly. It becomes less straightforward when the target is a 45-minute workout, a study routine or cooking dinner, because those episodes contain many actions that still require attention and adjustment.[Compass]compass.onlinelibrary.wiley.comOpen source on wiley.com.

Researchers therefore distinguish habitual instigation from habitual execution. Instigation means that a cue automatically prompts someone to begin: finishing work may generate an almost immediate impulse to change into gym clothes. Execution means that the subsequent sequence itself unfolds automatically. Research on exercise found that habitual instigation was more predictive of exercise frequency than habitual execution. In practical terms, the most useful habit may be “starting the workout automatically”, not performing every movement without deliberation.[PubMed]pubmed.ncbi.nlm.nih.govOpen source on nih.gov.

This distinction also resolves an apparent contradiction. Complex behaviours can plainly become routine — experienced runners go running, experienced cooks start dinner and regular students open their materials with little internal debate — yet the whole episode need not operate like an automatic reflex. Contemporary reviews describe complex behaviours as sequences in which some components can be habitually triggered while other components remain deliberate and responsive to changing circumstances.[Frontiers]frontiersin.orgOpen source on frontiersin.org.

That is often desirable. An exercise session should change when a person is injured or unusually tired. A study session should adapt to the material that proves difficult. A healthy meal cannot be prepared identically when ingredients, time and company change. For such behaviours, successful habit formation may mean automating the recurring gateways — starting, preparing or showing up — while retaining conscious control over the variable parts.[Compass]compass.onlinelibrary.wiley.comOpen source on wiley.com.

Why formation time varies so widely

Complexity is only one reason two apparently similar habits can develop at very different speeds. A 2024 systematic review and meta-analysis identified 20 experimental or quasi-experimental studies involving 2,601 participants. Only four studies directly supplied habit-formation times, which is an important limitation, but those studies showed striking dispersion: reported medians were 59–66 days, reported means included 106–154 days, and individual estimates ranged from 4 to 335 days. The authors concluded that behaviour type, frequency, timing, individual choice and other contextual factors all contributed to habit strength.[PubMed Central (PMC)]pmc.ncbi.nlm.nih.govOpen source on nih.gov.

Several factors are particularly relevant when the target behaviour has many moving parts.

Fewer usable repetitions can mean slower learning. Habit formation depends on repeated pairings between a context and an action. A behaviour performed several times a day generates many opportunities for that association to develop. A complex routine performed twice a week supplies far fewer repetitions over the same calendar period. The 2026 longitudinal study found behaviour frequency positively associated with habit strength, and frequency was the determinant whose interaction with time remained significant after correction for multiple statistical tests.[Sage Journals]journals.sagepub.comSage JournalsWhat Makes a Habit? Investigating Potential Determinants of Habit Formation - Sebastian Bürgler, Marina Milyavskaya, Gail Mc…

Variable circumstances weaken the consistency of the cue. Complex routines are more likely to move between places and times: one workout happens before work, another after dinner; one study session occurs at home, another on a train. A 2022 experiment and field study found that greater context stability predicted greater automaticity and better goal attainment. In the experimental arm, students deliberately building study habits either kept their time and place stable or varied them across six weeks. The overall findings favoured stable contexts, showing why a complex behaviour that occurs “whenever I can fit it in” may take longer to become automatically prompted.[PubMed Central (PMC)]pmc.ncbi.nlm.nih.govOpen source on nih.gov.

Preparation creates additional failure points. A single action requires one successful response to a cue. A higher-order routine may require several: buy vegetables, have ingredients available, begin cooking, prepare them and eat them. Research on the formation of a higher-order vegetable-consumption habit found that behavioural performance, perceived reward and context stability were all associated with habit strength between people, although the expected day-to-day causal pattern was not consistently observed. That mixed result is useful: real-life complex habit formation is not explained by repetition alone.[PubMed]pubmed.ncbi.nlm.nih.govOpen source on nih.gov.

Difficulty can change from one repetition to the next. A ten-minute reading habit is relatively standardised. “Go running for 40 minutes” can feel radically different depending on weather, fatigue, location and competing demands. The 2026 longitudinal analysis found perceived difficulty negatively associated with habit strength, alongside positive associations for autonomous motivation, frequency, context stability and positive feelings.[Sage Journals]journals.sagepub.comSage JournalsWhat Makes a Habit? Investigating Potential Determinants of Habit Formation - Sebastian Bürgler, Marina Milyavskaya, Gail Mc…

These factors interact. A difficult behaviour that is performed infrequently and under constantly changing circumstances provides a much poorer learning environment for automatic cue–response associations than a small behaviour performed every morning in the same place.

Setting realistic expectations

The most useful lesson is not that complex habits require a particular number of extra days. The evidence is nowhere near precise enough for a rule such as “simple habits take two months and complex habits take six”. The 2024 systematic review found only four studies that directly reported formation time, with substantial differences in designs and behaviours, and most studies in the wider review were judged to have a high risk of bias. Its estimated two-to-five-month window for health habits is therefore better treated as an indication that meaningful automaticity often takes months, not as a deadline.[PubMed Central (PMC)]pmc.ncbi.nlm.nih.govOpen source on nih.gov.

Even the researcher behind the widely repeated 66-day figure has warned against treating it as a universal prescription. In a 2026 University of Surrey interview, Lally stressed that the original study’s range of 18–254 days was more informative than the average because people and behaviours differed so greatly.[University of Surrey]surrey.ac.ukOpen source on surrey.ac.uk.

For a complex behaviour, a better progress question is therefore “Which part is becoming easier to start?” rather than “Has the whole routine become automatic yet?” Someone building an exercise routine might first notice that packing a kit and leaving for the gym requires less negotiation. A person trying to study consistently may begin opening the relevant material almost automatically after dinner even though the study itself remains mentally demanding. Those are meaningful signs of habit development because the recurring cue is increasingly controlling initiation.[PubMed]pubmed.ncbi.nlm.nih.govOpen source on nih.gov.

It can also make sense to reduce the unit being habitualised. “Cook nutritious meals every night” contains too much variability to offer one identical response to one cue. “At 6 pm, start preparing the planned dinner” is narrower. “Become organised” is not a repeatable action; “after finishing work, write tomorrow’s three priorities” is. This does not make the larger goal effortless, but it concentrates repetition on a stable, recognisable point in the behavioural sequence — exactly the sort of cue–action pairing habit theory predicts should strengthen with practice.[Compass]compass.onlinelibrary.wiley.comOpen source on wiley.com.

Occasional lapses should not automatically be interpreted as restarting from zero. In Lally and colleagues’ original study, missing a single opportunity did not materially derail the automaticity trajectory. What matters more is whether the behaviour repeatedly returns to the same relationship between cue and action. For complex routines, expecting flawless repetition can therefore be less useful than preserving the underlying pattern over a long enough period for learning to accumulate.[Wiley Online Library]onlinelibrary.wiley.comWiley Online LibraryHow are habits formed: Modelling habit formation in the real world - Lally - 2010 - European Journal of Social Psycho…

The broader implication for self-improvement is straightforward: demanding behaviours can become much easier to initiate and sustain without ever turning into completely mindless sequences. Complex habits often require more repetitions, more calendar time and more deliberate support because there is simply more that can vary. Success is not proved by reaching an arbitrary day count. It is visible when a stable cue increasingly pulls the person into the right behaviour with less deliberation — while the complicated parts that genuinely require judgement remain under conscious control.[Compass]compass.onlinelibrary.wiley.comOpen source on wiley.com.

Amazon book picks

Further Reading

Books and field guides related to Why Some Habits Take Far Longer Than Others. Use these as the next step if you want deeper reading beyond the article.

Book

Atomic Habits

By James Clear

Rating: 3.5/5 from 7 Google Books ratings

The #1 New York Times bestseller. Over 25 million copies sold! Translated into 60+ languages! Tiny Changes, Remarkable Results No matter...

See on Amazon

Book

Tiny Habits

By BJ Fogg

Improving your life is much easier than you think. Whether it’s losing weight, sleeping more, or restoring your work/life balance – the s...

See on Amazon

Book

Good Habits, Bad Habits

By Wendy Wood

'The world's leading expert on habits' - Matthew Syed, bestselling author of Black Box Thinking and Rebel IdeasWhat if you could harness...

See on Amazon

Book

The Power of Habit

By Charles Duhigg

Rating: 4.0/5 from 145 Google Books ratings

Duhigg takes us to the edge of scientific discoveries that explain why habits exist and how they can be changed. Distilling information i...

See on Amazon

Browse more on Amazon:Atomic HabitsTiny HabitsGood Habits, Bad Habits

As an Amazon Associate I earn from qualifying purchases.

eBay marketplace picks

Marketplace Samples

Live-tested eBay searches with available results related to this page.

Shop location

UsingUSA USA USAUKCanadaAustraliaIreland

Selected frommotivational poster oneBay.co.uk.

Current eBay listing

Motivational Quote Poster Wall Art Gym Office Bedroom Home Decor A4 A3 A5

GBP 9.99 | Free shippingNewSeller: old-school-soldier (99.6% positive)Ships from: GB

View listing on eBay

Current eBay listing

Gym Motivational Posters Work Out Insperational Quotes Wall Art

GBP 2.95 | Free shippingNewSeller: pixeldemonmg (99.8% positive)Ships from: GB

View listing on eBay

Current eBay listing

Motivational Quote Poster Wall Art Gym Office Bedroom Home Decor A4 A3 A5

GBP 9.99 | Free shippingNewSeller: old-school-soldier (99.6% positive)Ships from: GB

View listing on eBay

Current eBay listing

Motivational Quotes Framed Wall Art Poster Canvas Print Picture

GBP 24.95 | Shipping GBP 4.95NewSeller: pinkfeathers08 (98.3% positive)Ships from: GB

View listing on eBay

Browse more oneBay.co.uk

Example items shown for inspiration; availability and pricing can change. Branchoria may earn a commission if you purchase through outbound eBay links.

Endnotes

1. Source: onlinelibrary.wiley.com
Link:https://onlinelibrary.wiley.com/doi/10.1002/ejsp.674

2. Source: compass.onlinelibrary.wiley.com
Link:https://compass.onlinelibrary.wiley.com/doi/10.1111/spc3.12975

3. Source: compass.onlinelibrary.wiley.com
Link:https://compass.onlinelibrary.wiley.com/doi/full/10.1111/spc3.12975

4. Source: iaap-journals.onlinelibrary.wiley.com
Link:https://iaap-journals.onlinelibrary.wiley.com/doi/10.1111/aphw.12642

5. Source: iaap-journals.onlinelibrary.wiley.com
Link:https://iaap-journals.onlinelibrary.wiley.com/doi/10.1111/aphw.12597

6. Source: onlinelibrary.wiley.com
Link:https://onlinelibrary.wiley.com/doi/full/10.1111/jopy.12926

7. Source: onlinelibrary.wiley.com
Link:https://onlinelibrary.wiley.com/doi/abs/10.1111/jopy.12926

8. Source: onlinelibrary.wiley.com
Link:https://onlinelibrary.wiley.com/doi/abs/10.1002/ejsp.674

9. Source: onlinelibrary.wiley.com
Link:https://onlinelibrary.wiley.com/doi/abs/10.1002/ejsp.674?MixPanelId=15e3fe314440-0468d8411-64220f54-100000-15e3fe314460

10. Source: onlinelibrary.wiley.com
Link:https://onlinelibrary.wiley.com/doi/abs/10.1002/ejsp.674?source=content_type%3Areact%7Cfirst_level_url%3Aarticle%7Csection%3Amain_content%7Cbutton%3Abody_link

11. Source: onlinelibrary.wiley.com
Link:https://onlinelibrary.wiley.com/doi/abs/10.1002/ejsp.674?msockid=038ed114f43667dd0790c4bef5146634

12. Source: onlinelibrary.wiley.com
Link:https://onlinelibrary.wiley.com/doi/abs/10.1002/ejsp.674?cf_chl_jschl_tk=pmd_EwcJDaCFBR9OVEL1O_0qjioww0Gc86ZzpBvCBFhrDcE-1635261061-0-gqNtZGzNAjujcnBszQi9

13. Source: journals.sagepub.com
Link:https://journals.sagepub.com/doi/full/10.1177/01461672261440446

14. Source: pmc.ncbi.nlm.nih.gov
Link:https://pmc.ncbi.nlm.nih.gov/articles/PMC11641623/

15. Source: surrey.ac.uk
Link:https://www.surrey.ac.uk/news/does-it-really-take-66-days-form-habit-we-asked-expert-dr-pippa-lally

16. Source: pmc.ncbi.nlm.nih.gov
Link:https://pmc.ncbi.nlm.nih.gov/articles/PMC3505409/

Published: December 1, 2012

17. Source: pubmed.ncbi.nlm.nih.gov
Link:https://pubmed.ncbi.nlm.nih.gov/31396122/

18. Source: pmc.ncbi.nlm.nih.gov
Link:https://pmc.ncbi.nlm.nih.gov/articles/PMC4566897/

19. Source: pubmed.ncbi.nlm.nih.gov
Link:https://pubmed.ncbi.nlm.nih.gov/26148187/

20. Source: frontiersin.org
Link:https://www.frontiersin.org/journals/psychology/articles/10.3389/fpsyg.2021.626750/full

21. Source: pubmed.ncbi.nlm.nih.gov
Link:https://pubmed.ncbi.nlm.nih.gov/39685110/

22. Source: pmc.ncbi.nlm.nih.gov
Link:https://pmc.ncbi.nlm.nih.gov/articles/PMC9226889/

23. Source: pubmed.ncbi.nlm.nih.gov
Link:https://pubmed.ncbi.nlm.nih.gov/35756236/

24. Source: pubmed.ncbi.nlm.nih.gov
Link:https://pubmed.ncbi.nlm.nih.gov/35962435/

25. Source: pubmed.ncbi.nlm.nih.gov
Link:https://pubmed.ncbi.nlm.nih.gov/42053513/

26. Source: journals.sagepub.com
Link:https://journals.sagepub.com/doi/pdf/10.1177/01461672261440446?download=true

27. Source: journals.sagepub.com
Link:https://journals.sagepub.com/doi/10.1177/01461672261440446

28. Source: pmc.ncbi.nlm.nih.gov
Link:https://pmc.ncbi.nlm.nih.gov/articles/PMC13114073/

29. Source: pmc.ncbi.nlm.nih.gov
Link:https://pmc.ncbi.nlm.nih.gov/articles/PMC11920387/

30. Source: pmc.ncbi.nlm.nih.gov
Link:https://pmc.ncbi.nlm.nih.gov/articles/PMC11664030/

31. Source: pubmed.ncbi.nlm.nih.gov
Link:https://pubmed.ncbi.nlm.nih.gov/39702740/

32. Source: doi.org
Link:https://doi.org/10.3390/healthcare12232488

33. Source: pubmed.ncbi.nlm.nih.gov
Link:https://pubmed.ncbi.nlm.nih.gov/39489712/

34. Source: pubmed.ncbi.nlm.nih.gov
Link:https://pubmed.ncbi.nlm.nih.gov/39321606/

35. Source: pmc.ncbi.nlm.nih.gov
Link:https://pmc.ncbi.nlm.nih.gov/articles/PMC11351980/

36. Source: pmc.ncbi.nlm.nih.gov
Link:https://pmc.ncbi.nlm.nih.gov/articles/PMC11891988/

37. Source: pubmed.ncbi.nlm.nih.gov
Link:https://pubmed.ncbi.nlm.nih.gov/38450535/

38. Source: doi.org
Link:https://doi.org/10.1111/jopy.12926

39. Source: pubmed.ncbi.nlm.nih.gov
Link:https://pubmed.ncbi.nlm.nih.gov/37068252/

40. Source: pubmed.ncbi.nlm.nih.gov
Link:https://pubmed.ncbi.nlm.nih.gov/36771437/

41. Source: frontiersin.org
Link:https://www.frontiersin.org/journals/psychology/articles/10.3389/fpsyg.2022.883795/full

42. Source: pubmed.ncbi.nlm.nih.gov
Link:https://pubmed.ncbi.nlm.nih.gov/35580819/

43. Source: pmc.ncbi.nlm.nih.gov
Link:https://pmc.ncbi.nlm.nih.gov/articles/PMC7969808/

44. Source: pubmed.ncbi.nlm.nih.gov
Link:https://pubmed.ncbi.nlm.nih.gov/33746848/

45. Source: pubmed.ncbi.nlm.nih.gov
Link:https://pubmed.ncbi.nlm.nih.gov/33502088/

46. Source: pmc.ncbi.nlm.nih.gov
Link:https://pmc.ncbi.nlm.nih.gov/articles/PMC6960169/

47. Source: pmc.ncbi.nlm.nih.gov
Link:https://pmc.ncbi.nlm.nih.gov/articles/PMC6667662/

48. Source: frontiersin.org
Link:https://www.frontiersin.org/journals/psychology/articles/10.3389/fpsyg.2019.01556/full

49. Source: pubmed.ncbi.nlm.nih.gov
Link:https://pubmed.ncbi.nlm.nih.gov/23864536/

50. Source: pmc.ncbi.nlm.nih.gov
Link:https://pmc.ncbi.nlm.nih.gov/articles/3505409/

51. Source: pubmed.ncbi.nlm.nih.gov
Link:https://pubmed.ncbi.nlm.nih.gov/10174219/

52. Source: pubmed.ncbi.nlm.nih.gov
Link:https://pubmed.ncbi.nlm.nih.gov/36437536/

53. Source: surrey.ac.uk
Title: benjamin gardner
Link:https://www.surrey.ac.uk/people/benjamin-gardner

54. Source: surrey.ac.uk
Link:https://www.surrey.ac.uk/habitat-surrey-habit-application-and-theory-group/research/theory-and-methods

Additional References

55. Source: youtube.com
Title: How to Build Habits That Actually Last: A Neuroscience Approach
Link:https://www.youtube.com/watch?v=ObA4ne4TVsE

56. Source: youtube.com
Title: How To Break Bad Habits
Link:https://www.youtube.com/watch?v=0JJFaL4oaOA

57. Source: researchgate.net
Link:https://www.researchgate.net/publication/362509175_Habit_and_behavioural_complexity_habitual_instigation_and_execution_as_predictors_of_simple_and_complex_behaviours

58. Source: researchgate.net
Link:https://www.researchgate.net/publication/279807291_Habitual_Exercise_Instigation_vs_Execution_Predicts_Healthy_Adults%27_Exercise_Frequency

59. Source: researchgate.net
Link:https://www.researchgate.net/publication/336747494_Intervention_to_Modify_Habits_A_Scoping_Review

60. Source: researchgate.net
Link:https://www.researchgate.net/publication/386593213_Time_to_Form_a_Habit_A_Systematic_Review_and_Meta-Analysis_of_Health_Behaviour_Habit_Formation_and_Its_Determinants

61. Source: sciencedirect.com
Link:https://www.sciencedirect.com/science/article/pii/S2352154624000858

62. Source: tandfonline.com
Link:https://www.tandfonline.com/doi/full/10.1080/08870446.2021.2003362

63. Source: sciencedirect.com
Link:https://www.sciencedirect.com/science/article/pii/S1469029218305867

64. Source: zendy.io
Link:https://zendy.io/title/10.1002/ejsp.674