One of the scariest feelings in life is when you realize you aren't afraid to die.
You don't look when you cross the road anymore. When you take pills you take however many come out. You're not afraid when you hear those creepy creaking noises in your house anymore, because you hope they'll get you. You seek out dangerous things, because you want to die. You stop caring about yourself, totally and completely. Nothing about you matters anymore, and at some point you look at yourself and become scared of yourself. Because you're a monster, one who only hurts itself. And that's scary.