My folks quit smoking when I was 17 or so. My dad was fine, but my mom had a rough time of it. They've been smoke-free for almost 15 years, now, and are much happier (and wealthier) for it.
Four and a half years here as well. I was a chainsmoker of clove cigarettes, a habit picked up while adventuring in Indonesia. It is all about willpower. There is no need for any outside influence. Best of luck with it!