hmmm mel u know why u depressed???. I know it sounds like something everyone says, but everyone has down times and its helps the shape us as the people we are gonna be. BUt if its really bad please go get some help, we're here online and there is only SOOOOO much we can do.
I remember that phase when slicing ur arm was "fun" or calming but it should go away ( it should)
But if u can figure out what is bugging u , try to see if it can be fixed or solved. If it cant , then look for other reasons in life to be happy. I had my wrist slicing days about 3 yrs ago when i was 22 ( i had it before when i was 14) but i wised up and looked for my happy reasons, which were my dogs, and my best friend who was the only one who knew what i was doing ( mind u he's my BF now ).