Stress. Rule 8. They call stress a killer, and they are right. We're not talking about short term stress here like that person who cuts you off without a turn signal while they're chatting on their phone and you get really pissed. In fact, that kind of stress is natural (and some maintain it is actually healthy). It's chronic stress that is the problem. "Under chronic stress, adrenaline creates scars in your blood vessels that can cause a heart attack or stroke,” says Medina.