Yes I'm one of those smug "I quit smoking" people you just hate 'cos you can't right now.
Well I tried and tried for years. The determination was there, but wore off after a day or two.
And that's what it's all about, keeping that feeling of determination day, after miserable day, as each wave of craving comes on just as strong as the last. It ain't easy.
Here's something that helped me.
I compiled two lists "why I should smoke" and "why I shouldn't smoke" and I added to the lists every time I thought of something else and the "why I shouldn't smoke" list got very long indeed.
Then each time I felt the craving coming over me I whipped out the lists and read right through them slowly and carefully. By the time I had read to the end, the craving had wained and the determinaion was back.