To quit smoke. How?

[Kachamkin]

I smoked all my life - for decades. Three years ago I just felt the need to quit, - and I did it! I quit extremely lightly: no suffering, no withdrawal symptoms. Just smoked, - and stopped. I did not expect this to be so easy. I was disgusted with the smell of tobacco smoke, and I considered smokers with a slight contempt and some superiority: I could to do it and now I am free, while they remained slaves of dependence. And then three years passed, and again I need cigarettes. My body just has a great need for nicotine. And I understand that I won’t be able to quit now just easy for the second time, — it will require a very difficult fight with myself. I want to quit smoking - and I can’t. Perhaps some of you have come across such a situation, and can give useful advice. It's amazing how easy I quit three years ago, - and how hard it is for me to do it now. I would be grateful for any advice, your own experience in fighting with it, and for explaining why this is even could be possible.