Can you tell me if nail biting is considered as self mutilation, why isn't cutting your hair?

Symptom of anxiety: If there is a physical enjoyment of the discomfort it causes and a thrill from people looking at the damage then yes, but otherwise it is a sign of unresolved anxiety and generally feeling overwhelmed. I recommend starting a journal, spending an equal amount of time writing your hopes as writing your fears and then talk out these feelings and desires with a counselor or friend.