The 21/90 Rule: The Real Timeline for Habit Formation
The 21/90 rule is a popular claim that habits form in 21 days and stabilize by 90. This article explains what the rule gets right, what it gets wrong, and why real habit formation depends on behavior type, context, and repetition. It’s for readers building routines like exercise, sleep, or medication adherence who want a realistic timeline. You’ll learn how to track progress, design cues, and adjust when the “days” don’t match your experience.