My grandfather smoked his whole life. I was about 10 years old when my mother said to him "If you ever want to see your grandchildren graduate, you have to stop immediately." Tears welled up in his eyes when he realized what exactly was at stake. He gave it up immediately. Three years later he died of lung cancer. It was really sad and destroyed me.
My mother said to me "Please don't ever smoke. Don't put your family through the same thing your grandfather put us through." I agreed, and at the age of 28, I have never touched a cigarette. I must say, I feel a very slight sense of regret for never doing it because your post gave me cancer anyways.