I started smoking when I was 15. Quit a few times, always started again. Unfortunately I usually started again after a break-up with someone who made me quit. :/
I recently stopped again. I just stopped having cravings, out of no where. It's the same way I quit the last time.
I'm working hard to keep it this way. My mom passed away from lung cancer last Christmas Eve. 8 month downhill struggle, had to watch her suffer through all kinds of horrid treatments that make me question which causes more suffering; dying sooner of untreated cancer or suffering longer through torturous procedures and chemicals. I loved my mom, we were really close. She quit smoking three or four years before she was diagnosed with lung cancer.
My advice: QUIT now, while you're young. The longer you wait the harder it gets and even if you do, you can still become diagnosed with cancer.