As a former smoker for 20+ years, I can attest to all the BS the mind puts you through as you march from one quit attempt to the next. Patches, gum, zyban . . . made no difference.
For me, the dx of cancer was the end. There was no wiggle room for the brain this time. Done. Put 'em down and haven't touched one since. No cravings, no weight gain (though probably invisible in light of weight loss during treatment), no nothing. My focus on my treatment was so intense that I really did not think about the smoking at all.
I probably think more about having a cigarette today than I did during treatment, simply because my mind is not as focused elsewhere. Still not an option to pick up the cigarette.
Motivation is the key. You have to snap that mindset that says you can't to the mindset that you have to. For me, unfortunately, it took a cancer diagnosis to get me to that point, but am glad I did. All part of maximizing my chances to beat this thing.