Dear Amby,
After reading your post I wanted to give you advice from a previous self-harmer(Not that I am proud of it, its simply the truth). Let me first give you a quick backstory: I myself was a self harmer and I would have moments of rage, self loathe, and various other negative emotions that would fuel me to self harm. The way that I stopped was by first finding out what started my emotions and found an outlet to it. For example I was filled with so much rage that I cut, bruised, and even considered burning at some point. So after a while I hated the habit that I developed so I instead threw away all the objects that I even considered using to harm myself with then I found something that I either loved or something that helped me release that pent up emotion. I tried martial arts and now I can just channel that emotion out through physical exercise. My advice for you is to just find a way to let out that emotion without causing harm to yourself or others. And really realize that even if times are hard you have to keep pushing through them so that one day you can reach that moment of happiness.