I started at 14 because it was "cool", then stopped again at 16. I started dating a smoker at 22, and soon was back on 40 a day. I decided in mid-February 2001 that it was time to stop and haven't had another one since then.
The thought of giving up was harder for me to deal with than actually stopping. Once I'd made my mind up that I would it was a lot easier. The worst part was finding something to do with my hands. I had a few months where I was constantly tapping pens on the desk and chewing the ends of them, but apart from that, I didn't really suffer much at all. I don't think I was even more bad-tempered than usual. Mind you, that was about the time when I started working from home and didn't have to face my boss every day. That's enough to improve anyone's mood!
Now, smoking doesn't bother me at all. I can think of three times when I've thought, "I wouldn't mind a cigarette now," but i wasn't a case of having a craving, it was more like remembering a similar time when I'd enjoyed a cigarette in the past.
I must admit though, I don't feel any healthier having stopped than I did before.