(((InACorner))) I know what you mean, I feel like my own worst enemy sometimes. I don't know how to help with the self harm, sorry, but as for beating yourself up verbally...if you find yourself thinking things like "I'm useless" or "I can't do anything", then try and think of examples of things you can do to prove yourself wrong. Nobody is completely useless, everyone has something they're good at! You could try taking a look at the "Steps To Better Self-Esteem" forum as well.

Hope some of that was useful.