Building a habit of quitting is much harder than building a positive habit. When I talk about a positive habit, I'm talking about, for instance, doing pushups every morning when you wake up. It's a definite action. When you wake up, you do some pushups, then you know you're done. Even if you do it later in the day, that's a kind of success.
To quit something is a much more empty kind of act. Say you're quitting smoking. Today, you throw out your cigarettes and don't buy more, but the victory is when, every single time the urge to smoke rises up, you do nothing. Then tomorrow, when you want to smoke, you do nothing. You continue doing nothing until, hopefully, eventually, the urge to smoke doesn't come up again, and "not smoking" is no longer a goal or a victory but your default state of being. There are certainly rewards to quitting something destructive like that, but they're less tangible and more long-term than the satisfaction and reward of doing something positive.
Perhaps that's something to consider. Instead of aiming just to quit something, you should aim to take up something positive instead, like the pushups. Maybe, eventually, you will associate the same triggers with an urge to do some pushups instead of an urge to smoke. I'd like to see that clinical trial.
Mokalus of Borg
PS - I'm sure it's been done.
PPS - It seems to be common enough advice, anyway.