Do something that you like. If you don't have a hobby or likewise, try finding one. Whenever I get depressed I ride my motorcycle. You just don't have time to think negatively while you're filled with adrenaline and on a bike. I've also met some very close friends by simply riding my motorcycle. For example, I met one of my best friends when I was biking to the sea because I had nothing to do. He was doing the same thing, so he followed me and we started to chat. That's just how it worked for me, but if you find a hobby that's works for you, spend some time on it whenever you start thinking negatively.