For what that's worth, when I quit smoking, I didn't feel any withdrawal symptoms except being a bit nervous and irritable for a single day (and I'm not even sure if quitting was the cause, since it coincided with some stressful issues at work that could well have caused it regardless). That was after a few years of smoking something like two packs a week on average (and much more than that during holidays and other periods when I went out a lot).

From my experience, as well as what I observed from several people I know very well, most of what is nowadays widely believed about addiction is a myth.