I have many bad habits. My absolute top-success in overcoming them was getting rid of smoking cigs. And I really mean, getting rid of it, even in my thinking. You see, the nicotine addiction is just the minor part in smoking, it is not that hard, other drugs are harder to get rid of in my experience. But the manipulation in your thinking that comes with years-long smoking, that is astonishing. And the main factor that makes it hard to quit smoking is a deep fear that life will never again be as awesome as it was with the cigs (even if the smoking destroys so much life moments all the time).
I got rid of it by reading the book "Easy way out" by Allen Carr. I highly recommend his stuff. I did read the book 3 times in a row until all the thinking damage in my head was gone. But then it was gone and after smoking heavily for 8 years I am now out for over 6 years.
If you think about quitting smoking, try Allen Carrs method, I truly recommend it, from man to man ;-)