Ask your parents' permission before doing what I say. If they said yes, do it. If they said no, just read.
Go up to a lit candle. Hold your hand to the side, and very quickly brush your hand through the flame (be fast!). You didn't get burned, did you? Now do it over and over, but don't slow down. Look at your hand. It may be a little gray or black. (You can stop now.)
When we're with people who try and tempt us, the first little thing we do might not hurt us, if it's little. But then we do it again. And again. And our hearts start turning gray or black. What we're doing is slowly harming us, and the more we do it, the worse off we are. Or, in the other scenario, you get cocky after the first little thing and move onto bigger things (say, a fireplace) and you get burned, maybe deformed. It burns, it hurts, and there might be permanent damage.
When you stick your hand in the fire, sooner or later, you'll get burned. So why not just stop doing it? Why not just resist? That temptation may give you a thrill for a moment, but the thrill is fleeting and the damage can be permanent. DON'T fall in the trap. Keep away from the fire.
See what I'm talking about? Let's take smoking, for instance. "One little smoke won't hurt you. No one will ever know." Yeah, right. Your parents will find out, and so will your friends. You might have trouble breathing and you, your room, and your belongings will smell like smoke. You'll probably get addicted to smoking and you'll do it more and more. Then, ten years later, the news hits you like a baseball bat. You've got lung cancer. Oh, joy. What now? Don't stick your hand in the fire. It is soooooooooooo not worth it.