Myth 6: It takes 21 days to break a bad habit (or form a new one).
Fact: Popular self-help gurus and many diet plans claim that it will take 21 days to form a new healthy habit — or break a bad one. The truth is, there is no magical time frame for breaking bad habits. One study that evaluated behavior change found that creating a new habit, like eating a piece of fruit daily, took an average of 66 days. However, there were wide variations — anywhere from 18 days to 254 days. The authors found the adaptation time was a function of how hard the new behavior is as well as the individual. If you're trying something new, like daily exercise, give yourself time to make it a routine. It may not happen overnight — or even in 21 days!