If you really feel like a waste of space, get yourself some help and change that; become some one of worth. Go do something with that "miserable" life of yours: go volunteer, get in shape, finish school. Do what makes you happy and fuck everyone else, but DO NOT fuck anyone else over. >I'm only saying this as a friend.
You can sit around feeling sorry for yourself, waiting to die and disappear hoping no one remembers who you are or you can do something about it and prove everybody else wrong. You can be the difference in someone else's life, and even in your own.
I'm not saying it's not okay to be depressed, or to feel down. I've been dealing with Clinical/Manic Depression and BiPolar for 8 or 9 years now, and let me tell you. I understand how much it fucking sucks. I've been without medication for a few weeks now and I feel like I could go off the deepend at any moment.
This isn't about me though, it's about you. I can promise you, it's all in your head. You can't change the events that happen to you but you can change the way you handle them, what lessons you learn and how you advance forward with your life.
I hope this helps someone reading this. No one can save you but yourself if you don't want to be saved; you better believe you have no one else to blame but yourself for never fighting back.