Some very fortunate people can remain "social smokers" and some can't. I think I had a lot of trouble with it because I was very young when I started, 13ish, so my body grew up on cigarettes and as long as I'd been an adult every last cell for those last 2 or so growth spurts came into creation in a body system functioning on nicotine. It was bad, and I dreamed about smoking for a year or two after psychologically, too. Your Nan was probably also put on an anti-depressant as part the medications for her heart attack recovery, which curbs the withdrawl symptoms and is pretty standard with doctors to help people with sudden health traumas like heart attacks and strokes


When you're ready to quit, and when the right motivation is there and it's the right time for the individual it can be done, like kicking any substance and/or habit. Some people that never happens for though, and it certainly isn't accomplished on demand. It's not any animals natural instinct to inhale smoke, and honestly my advice is to not try those first few times to counter that instinct because like any habit it creeps up on you.