Think it'll take 21 days to make your resolution a habit? Try tripling that

Whatever it is you've resolved to do in the new year - floss! Become an a.m. exerciser! Stop the late-night snacking! - the conventional wisdom is that it'll take 21 days to make the new behavior a habit.

http://www.nbcnews.com/health/think-itll-take-21-days-make-your-resolution-habit-try-2D11826051