At least, that's been my experience. You try to have self-control over something and you fail. You try again and you fail. You try again and you fail. And then gradually, all those tries add up to greater amounts of self-control than you had in the past.

So if you trip again (crosses fingers that you won't, since this is a part of your life you want to change), just keep in mind that each try will take you closer to your goal.