Awareness leads to compassion. Will power leads to competition.

Whatever you don't want to do but do anyway, do with awareness. Whatever you don't want to feel but feel anyway, feel with awareness. And finally, whatever you don't want to think but think anyway, think with awareness. When you "get it" for real you'll probably have had enough of whatever it is you don't want anymore.

The awareness of having had enough comes with the breathing, slow aware breathing. Take a few deep breaths during the moment, relax, be aware, and let whatever it is be felt. Repeat this as many times as you need, and if it doesn't feel bad, then you might consider not stopping what you thought you should stop. Maybe the benefits are greater than from stopping. Think about the benefits it brings, whatever you do that you think you shouldn't do. If it takes time, let it take time. Just breathe, and feel, while you do it.

Source: http://kellymcgonigal.com/books/