If the substance is subsequently not available, a smoking addict start to have withdrawal symptoms as the body has to readjust itself to function without the substances. It's been found that most of the youngsters start the habit of smoking by observing their friends, relatives or other elder people whom they are get used to everyday.

Youngsters make it a habit, as a revenging mentality toward their parents. The youngsters of these days are too sensitive, they don't need anyone to advise or oppose them. If anyone does so, they take it as great issue, and continue with the things, which they thing that their parents don't like. It's a genuine reason for addiction.
Teens, there is nothing to feel wrong with what your elders are telling you, just a proverb to you all "look before you leap".