Today I decided to cut up my arm a little.
Why would you harm yourself?
I just did it to relax
You need to get help from someone. That isn't a healthy thing to do and will cause you a lot of pain and these cuts could get infected.
My self esteem is low
That's why you need to go to therapy or find someone to speak with. Cutting yourself up will eventually lead you to doing even worse things until you can't take it back.