My Galactic Battle Base story I'm writing right now is about a 16 year old girl who cuts herself and her boyfriend who deals drugs and was the victim of childhood sexual abuse. (And a creature who wants to feed off of them.)
My background research is mainly on a Tumblr blog where I follow a lot of depressed teens who cut, have eating disorders, and consider suicide. Everything they post is mostly black with white writing.
Talking with Lisa Carroll Peterson the other day, she pointed out that the Gay Mantra "It gets better" applies to them as well. If they could just make it through the next ten years they will find themselves in a niche of friends, jobs, and activities where they feel accepted for who they are.
I believe what they need to do to feel better about themselves, and thus survive early adulthood, is find a way to serve other people. Sacrificing yourself to help another is the only way to find self esteem.
However, if your problem is co-dependence, have a therapist help you find a way to serve.