For anything you wish you were doing every day, like working out or practicing violin or working on your startup: Get a big, yearlong calendar and put it on a wall in your bedroom. Every day you complete your task, mark a big, red "X". Eventually, you'll build up a big string of X's and won't want to break it. That incentive will push you more than you think.
I'm having a decent month: http://calendaraboutnothing.com/~telemachus
Worked much better than the excel spreadsheet I had tried before (the one from the Hacker's diet).
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!
From this I'd gathered that tooth discoloration is permanent.