How long does a new habit take?

You may have heard that a habit takes 21 days. A study at University College London followed people building new daily habits and found it took 66 days on average, with a range from 18 to 254 days. Missing a single day didn't undo the progress.

That's why both books use a 4-week plan as a start, not a finish line. The aim is to make sorting your voices feel normal, then keep going until it happens on its own.

Source: Lally et al., European Journal of Social Psychology, 2010.