Well I can't really talk about smoking too much, because I was never a heavy smoker. I only smoked about 2 packs a week and that was mainly because of the culture @ my retail job. Once I quit it wasn't smooth sailing, but compared to the trials of heavy decade(s) long smokers it was a breeze. I have however broken other addictions that were heavy and ingrained by years of indulging. The advice that I'd offer would be to quit as often and as long as possible. If you quit for a while and then buy a pack and get sick of yourself 2 cigarettes in, go throw it away while you have the willpower. Never mind the money. It's worth it. Every time you don't smoke is a change for the better. And if you do find yourself in a position where you're smoking again, just make sure you're trying to smoke less than before. If you could cut use by one cigarette per day each week (meaning the first week you smoke 40 cigs a day and the second you smoke 39 a day) then I'd consider that great progress.
Now I understand that this is sort of rosy lensed advice so let me offer a different perspective. Failure is almost inevitable. Not saying you can't go cold turkey and never go back, but this is just my two cents. There's a difference between a failure and a loss. When you lose, the game is over and that's it. When you fail, you get to pick yourself up and try again. It can be overwhelming to think that I need to be A and not B. There's a lot of room between A and B, or smoker and non smoker. To me, the better perspective is, I need to be better. That perspective allows for failure. We need failure to succeed. It's a big part of the learning curve. So just *try* to do better. And when you find yourself with a cigarette in your mouth realize that you didn't do better this time, but it's no big loss, because you can do better next time.
As for the OP, I'm rooting for you, I know it's difficult to give up a habit like smoking.