The Straight Line Myth: Why Real Change Looks Messier Than Your Project Plan

Publish date: Friday, September 18, 2026 | Category: Counselling | Read time: 6 min read | Author: Carolyn Charest, MC, R.Psych

You may have heard that it takes 21 days to build a habit, but people do not form habits in an exact number of days. You decide this is the month you get back to regular workouts, stop checking work messages in bed, or quit saying yes to everything people ask of you. Three good weeks go by, then you hit a deadline in the same week as a sick child, a family visit, or a few nights of poor sleep, and by week five the old routine is back and you are wondering why you bothered. Most of us expect personal change to work like a progress bar that fills steadily from left to right. Researchers who study how people change have found something much closer to a squiggle, and if you know that in advance, you are less likely to abandon a good goal after one bad week.

The stages of change model was always a spiral

Years ago I worked on a smokers' helpline, and the framework we used with every caller was the stages of change model described by Prochaska et al. (1992). The model has five stages: not yet thinking about it, thinking about it, preparing, taking action, and maintaining. A list like that reads as sequential, with each stage leading to the next. The authors drew the model as a spiral, and that matched what I heard on the phones, because many callers were often on their third or fourth quit attempt. Their research found that moving straight through the stages was possible but relatively rare, and that people often relapsed along the way. Among smokers who were quitting on their own, about 85% of those who relapsed went back to thinking about or preparing for their next attempt, and only about 15% returned to square one. Put simply, most people who slipped went back a step or two and very few lost all the ground they had gained.

Expect jumps, dips, and plateaus

Hayes et al. (2007) pointed out that therapy researchers had long assumed people get better slowly and steadily. Many studies only measured people before and after treatment, so they missed everything that happened in between. When researchers tracked people session by session they found other patterns. One of those patterns is the sudden gain, which is a large improvement between one session and the next that holds. Lemmens et al. (2021) reported that about 40% of people treated for depression have one, with a range of roughly 26% to 50%. Many people in therapy make a big part of their progress in one jump between two sessions, and they do not get a little better each week at an even pace.

A rough patch can be part of getting better. In their own trial of a therapy for depression, Hayes et al. (2007) found that some clients felt sharply worse partway through treatment and then recovered, and those clients had improved more by the end of treatment. Their journal writing from those hard weeks also showed bigger shifts in how they saw and felt about their problems than the writing of clients who never had a rough patch. Hayes and colleagues added that people often go through an unsettled period right before a lasting shift. If you feel awkward saying no, or keep bouncing between your old routine and your new one, you may be in that unsettled stretch of time and one hard week does not mean that you have failed.

Habits take longer than you think, and you can afford a missed day

Lally et al. (2010) asked 96 volunteers to repeat one new eating, drinking, or activity behaviour every day for 12 weeks, such as eating a piece of fruit with lunch. For the 39 people whose results fit the researchers' model, the estimated time for the behaviour to feel automatic ranged from 18 to 254 days, with half of them getting there within 66 days. People who missed a single day lost no meaningful ground. They also made their largest gains early and then levelled off. If you hit a plateau in month two, it is possible that you are seeing the normal shape of the curve and your discipline is fine.

What you do after the slip matters most

High achievers tend to meet a setback with a harsh internal performance review, on the theory that criticizing themselves will keep their standards high. Breines and Chen (2012) ran four experiments on the opposite approach. They prompted some people to treat a personal failure or weakness with self compassion, and they compared them with people prompted to boost their self esteem and with people who got a distraction or no prompt at all. The self compassion group spent more time studying for a difficult test after failing the first one. In a separate experiment, they reported more motivation to make amends for a recent wrongdoing and to avoid repeating it. The authors called the result somewhat paradoxical, because the people who accepted their weaknesses were the ones more motivated to improve.

let go of the straight line

People who make a lasting change usually go through a false start, a plateau, a surprising jump, and at least one week they would prefer to forget. If you are in one of those right now, you are in the middle of the change process, which is exactly where you do the work.

References

Breines, J. G., & Chen, S. (2012). Self-compassion increases self-improvement motivation. Personality and Social Psychology Bulletin, 38(9), 1133–1143. https://doi.org/10.1177/0146167212445599

Hayes, A. M., Laurenceau, J.-P., Feldman, G., Strauss, J. L., & Cardaciotto, L. (2007). Change is not always linear: The study of nonlinear and discontinuous patterns of change in psychotherapy. Clinical Psychology Review, 27(6), 715–723. https://doi.org/10.1016/j.cpr.2007.01.008

Lally, P., van Jaarsveld, C. H. M., Potts, H. W. W., & Wardle, J. (2010). How are habits formed: Modelling habit formation in the real world. European Journal of Social Psychology, 40(6), 998–1009. https://doi.org/10.1002/ejsp.674

Lemmens, L. H. J. M., DeRubeis, R. J., Tang, T. Z., Schulte-Strathaus, J. C. C., & Huibers, M. J. H. (2021). Therapy processes associated with sudden gains in cognitive therapy for depression: Exploring therapeutic changes in the sessions surrounding the gains. Frontiers in Psychiatry, 12, Article 576432. https://doi.org/10.3389/fpsyt.2021.576432

Prochaska, J. O., DiClemente, C. C., & Norcross, J. C. (1992). In search of how people change: Applications to addictive behaviors. American Psychologist, 47(9), 1102–1114. https://doi.org/10.1037/0003-066X.47.9.1102