I quit cold turkey, too, but reading occasionally Allen Carr's Easyway, which helped a lot to recognize the thought processes I had concerning smoking, why it was so hard to quit, what actually made me want to smoke and so on. Treating the physical addiction is pretty simple, in the end - it's the mental side that's hard, and the book helped with that.
The hardest part was realising I could never ever smoke again, not even a bit, not even once - I'd just slip right back in one tiny bit at a time. Silly, huh, why would I even want to smoke again? It smells and tastes so bad now (although I know of course that it would start to smell and taste good if I went back, but it would take a while). So silly why it feels so difficult, knowing you can never do something again, even when you know it's not good for you at all and isn't actually even that enjoyable. Well, not anymore, haven't smoked for maybe five or six years now? But the first year or two was occasionally pretty hard, the worst part being the first few months.