If you've wanted to break a bad habit or addiction, like smoking, one way to do it is to re-write your thoughts. Smokefree.org suggests that "smoky thinking" (meaning the act of thinking like a smoker) makes it harder to quit, and that you need to think differently if you're serious about quitting. This advice applies to more than just smoking. If quitting is your goal, it may be time to change the way you think.
Photo by andyket
Personally, I can't stand cigarettes. I've never tried one because I've always found the smell and the idea of them so repulsive that I just don't want to be anywhere near them. I know some smokers find the way I think about their habit to be pretty obnoxious, but the way I see it is exactly how you need to think if you want to quit. You need to see the act as bad and harmful in every way possible—especially to your goal of cutting it out of your life.
Smokefree.org says you need to replace thoughts like "I just need one cigarette to take the edge off these cravings" with "even just one puff will feed the cravings and make them stronger." Obviously you can't stop yourself from thinking how much you want a cigarette, but you can stop those thoughts when they happen and instead say something that will help you, like with the aforementioned example.
This doesn't have to apply only to smoking. Whether you bite your nails or eat unhealthy foods, if you train yourself to think differently about your actions you may just have an easier time cutting out your bad habits.