I have a theory. People who suffer from a disorder don't want to get better. Not because they like the way they are, but because it's the only feeling they know and deal with in some way. It's comforting, it's something constant, unchanging, something you know and understand. You can't always rationalize it. But that's just the way it is.
3..
Why do people destroy themselves?
I don't know if you can say that people willingly destroy themselves. They do things that help and comfort them. They do things to distract themselves or to forget. Most of the time they know it's wrong but they still choose to do it. It all starts with just trying. Maybe someone will suggest it to you or you'll see people who deal that way. And then you just try it. Just once. That's not gonna hurt anybody, right? No one will know. And that's exactly how addictions are created. People crave that feeling of euphoria. They crave understanding or comfort. It can be harmless, like biting their nails or lips. At worse, people will put a razor to their wrist and say "one last time." The person in question may stay awake or refuse food, or instead eat to fill the void. They can practice until they pass out, until they feel every muscle in their body give out. They can read and lose touch with reality, losing themselves in other people's stories instead of dealing with their own problems. And then, of course, substance abuse. Drinking to the point where you feel dizzy and don't know where you are. Inhaling cigarette smoke or smoking pot. Doing drugs or just mindlessly swallowing pills hoping you'll forget. Finding comfort in other people. The ones you just met. You want to feel loved or you don't want to feel anything at all. You want to fill the void. People destroy themselves because they think it will help them. But deep down, they know these things will only make it worse because you'll crave them more and more. People destroy themselves because they feel too much or nothing at all.