I smoked from about age 12 to age 18, regularly from about age 13.
I quit [almost] cold turkey when I found out I was pregnant at age 18. After I found out I was pregnant I smoked maybe 8-10 Marlboro menthol light cigarettes - and most of the time I wasn't even smoking a full cigarette, but sharing with my boyfriend. Not that it is any more justified. He quit too, but still has problems to this day. I guess it wasn't as much of a motivation for him as it was for me.
I have had 2 cigarettes since I had my son and quit breastfeeding when he was 15 months. Last semester during school, I don't know why - I had bought a pack of cigarettes, I think because during my night classes at break time almost everyone would go outside and have a smoke. I'd go outside too, to make a phone call or just to get out into the cool night air, and being around them all the time I wanted to see what it was like again. I smoked 2 cigarettes (separate nights) and felt disgusted with myself so I threw the whole pack and my lighter away.