Invulnerability.

We forget what it's like to be teens. We forget that teens don't think anything bad will happen to them. They won't die and their parents won't die and they won't be hurt badly or have to suffer from uncurable diseases.

Witness skateboards and half-pipes, drugs and alcohol, driving while intoxicated or racing or driving wildly just to get the girls excited. They engage in sex because they witness it in every story they see (where noone suffers for it and not one character stops mid make-out for a condom) and because their hormones are racing and it doesn't worry them that they might get AIDS or another STD or pregnant, because they see themselves as individuals, apart from statistics. Even if they did see the statistics, they think they will be the exceptions, not the rule.

Remember how we thought our first boyfriends would be our last? We would love them forever and we could get married and survive life or when they broke our hearts, we thought we would never survive?

It isn't until later, when we get caught by our bad behavior through our own experience or one of a close friend, do we begin to understand that something unwanted, something bad could happen to us and perhaps we might want to consider elbow and wrist pads or calling our parents when we are drunk or using protection.

Teen don't know that they are vulnerable and that's a strong enough reason to play with the fire.