I've been smoke free for 23 years. Before that, I had a 40 pack-year history.
It took me 5 tries to finally quit. The first 4 I used nicotine gum. The last time was cold turkey and it worked.
There are two parts to nicotine addiction: Physical and psychological. As long as you keep introducing nicotine into your body, you'll keep craving it. The psychological part has to do with how firmly you think of yourself as a smoker.
In my case, the thought of never having a smoke again would put me into a panic. I found I was able to quit by focusing on one day at a time. Every morning I'd look at myself in the mirror and make a promise that for that day and that day only, I would not smoke. After about 3 weeks, I realized I had gone a whole day without thinking of smoking. After about 3 months, I would go for a week or more without thinking of smoking.
Just hang in there. If you're successful, it will be one of the hardest things you've ever done. But when you've succeeded, you'll realize you're better than smokers and non-smokers alike. You're better than smokers because you've quit. And you're better than non-smoker because you got hooked and still quit.