I won't say that I understand, simply because I was a casual smoker; beer in one hand, cigarette in the other ... or when I was with friends who smoked ... or when I was really stressed out.... I didn't really have any trouble 'quiting.' I still occasionally get the urge to have a cigarette, or dream about having one. That's something that never really goes away from what I've heard.
My grandmother smoked for 60 years. She quit when she was 82 because her sister had to quit - gave it up just like that, no problem. Weird huh?
I've always wondered how women can quit smoking while they are pregnant, but go back to it once the baby is born. It doesn't make any sense to me. Obviously it's healthier for the child if mom stays smoke free (dad too!), even after the baby is out of the womb. All I can offer is moral support, and hugs.