Well, multiple reasons, one has to do with control. When we feel we have to control over our lives and the direction it is headed, we self-injure as a way to take perceived control, as in "I can control what I do with my own body at least." But that idea is a façade. You are actually losing control when you self-injure. Another reason has to do with not having a coping mechanism to deal with a flood of overwhelming emotions. The concept of cutting when in pain is actually more universal than one might think. A lot of tribal cultures self-mutilate after the death of a loved one to show that they are grieving. I think that people want the internal pain to match their external. It's a way of crying out for help. But it isn't healthy. It's an endless cycle. When you self-mutilate you create a permanent reminder of your pain - and then looking at the scars will take you back to the same state - as in, "oh my, I can't believe what I did to myself" and make you want to cut again because you can't contain the guilt that you feel - when instead you should focus more on the positives and not sink into the cycle. Once you start, it can be very difficult to stop. I suggest finding alternative/healthy coping mechanisms, such as writing as a form of release, or exercising when you feel depressed, or any other hobby that sparks passion in you and that you find stress-relieving. It helps more than you know. Take that emotion and direct it toward something more productive and healthy that you can feel good about.