When I'm angry, why do I always feel the need to hurt myself?

its a common way for people to take out their anger or sadness, to take it out on themselves, its quite dangerous to do

Most often than not the easiest way to get rid of frustration is to either cry or to take it out on self... i'm not saying its right but we do it because subconsciously we think the root cause of our anger is nobody but our own actions... its an instant release of emotions and also a form of sympathy. So we know what has triggered the emotion... how do we control it??? Very simple... Every time you are angry convert the destructive energy into constructive energy... get on the treadmill or jog for 30 mins or pull out a canvas and splash it with colors. This not only calms you but heals you too... worked for me , hope it works for u :)

Perhaps because the anger you feel gets a bit lost in transit (if you follow) and ends up without a direction or outlet of any kind. Anger that isn't expressed in a way that deals with it positively - like through creativity, exercise or even by finding a secluded place and screaming about it - can build up to the point where it doesn't matter what caused it, it's there and needs an escape. Unfortunately some people find the easiest or most effective escape to be through some kind of pain. That's one theory I suppose.

Because you have so much anger inside that you body feels the need to let it out in a unhealthy matter

If you're suffering mental health issues, one of the major issues is loss of control. Self-harming when you're mentally unwell/angry, etc, is a form of control. You can't control what's happening around you, but your subconscious believes that YOU'RE in control by harming yourself. So, if you can't control the outside world, you'll turn it inward.

I don't want to hurt others and the anger I feel sometimes is directed at myself and I feel the need to hurt myself because it feels like I deserve it

Because it feel like it is the last resort and it is the only way to escape. Try not to cut and go and chat how you feel and this may stop you from cutting.

You may feel the need to hurt yourself because of the sudden relief of anger when you hurt yourself the pain you feel over rides the anger making you feel better

Sometimes, one can get mad at themselves & hurt themselves in an attempt to punish themselves. When one is angry at a loved one, sometimes we hurt ourselves to show a sort of punishment for getting angry at a loved one.

you have to learn one thing: hurting yourself is not good. i also cutted my wrists and i also thought i was helpful. but it isnt. when you're angry, you want to hurt someone and this "someone" is usually you.