I have enough control to not take it out on friends/people I don't know, but with family it's different. Little things they do set me off when I am in a low period. I put holes through walls, verbally attack my parents, and mouth off.

Usually, my parents either avoid it, or face it with consequences. When I put holes in walls, I am expected to pay for plaster and paint to cover it up, and spend time doing that.

When I get to a self-destructive phase, my parents won't let me be alone. They usually know thats where I am at when I start picking skin off my fingers (until they bleed). I guess I should thank them for that, but it's so annoying at the time that they care about me to do that. Does that make sense?

Not sure what to say about your friend... it's hard to face destructive behaviors. Sometimes, even though it's hard, you have to be selfish and think whats best for you. I always feel bad thinking "whats best for me in this situation" because I always try to "save the world".