The most powerful brain function is association, it affects your impulses and desires.
You've always associated smoking, the actual action of drawing smoke into your mouth, as a pleasurable experience, thus, you will find it hard to stop.
Before going cold turkey, smoke as many cigs as you can manage, taking a drag every 3-5 seconds, it's not nice, you get the proper ash tray taste, and a burning in your chest from constant hot smoke and lack of fresh air.
For best results, do this a few times before you go cold turkey. Once you've gone cold turkey, any time you get a craving, just remember what the last one was like, the disgusting taste and burning chest: why would you want one of them?
Obviously you can't do that now, but if you ever defect back to them, then try it.
FYI, I have never smoked, but I saw that method on TV, and it's quite logical, and worked wonders on the subjects.