I am not as happy as I used to be.?

It seems like things aren't as exciting as they used to be, such as parties, friends, family, etc. The only thing that excites me now is good music. I miss being excited from seeing one of my friends in school like the good old days. But I think my happiness might be from people constantly putting me down telling me that I will never amount to anything and I might as well kill myself. From thi, I now have low self-esteem which makes me look at myself differently in the mirror everyday that I look at myself. What should I do so that I can get my old, happy-go-lucky self back.