I used to have really yellow teeth because I brushed my teeth really rarely (thank goodness I never smoked). I've had some periods where I brushed them more often but I'd quickly fall back into hopelessness.

Then I hung a small calendar in the bathroom where I cross each day that I brush my teeth, and the "I don't want to break my win streak" feeling is so RIDICULOUSLY compelling that it's been many months now and I brush my teeth almost every day, in fact I didn't miss one day since 1 month and 3 weeks ago.

DON'T underestimate the sheer POWER of "win streaks".

My teeth are almost white now!