Habits take about two months to form, not 21 days
What they found
A new behaviour becomes automatic in about two months, not the popular 21 days - the median here was 66 days. The real story is the spread.
How they know
96 people chose one daily habit (a food, a drink, a short walk) and rated how automatic it felt every day for 12 weeks; researchers fitted a curve to each person.
What it means for you
Give a new habit two months before you judge it, and do not quit over a missed day - a single lapse barely dented the curve.
The limits
Simple daily behaviours only, 96 people; the individual range ran from 18 to 254 days, and harder habits likely take longer.
This is a short takeaway in our own words, not a reproduction of the study. For the method, the sample and the caveats, read the original. Mind lives inside the Booking Minds app under the brain icon, where you can save and share each piece.