What are some good coping mechanisms ?

I've been self-harming for 9 years and the basic coping mechanisms that people tell you to use don't work for me at all. In my opinion, the ice one is hilarious since where are you going to get the ice if you're not at home?! , When I self-harm, it's because I need to get rid of a certain feeling as if it's under my skin. I've also discovered that sometimes breaking objects works as well, but it doesn't completely remove that feeling. My friend is trying to help me a lot with this and suggested squeezing my hands into a fist, but I'm afraid I'll end up punching something and hurting my knuckles.