Best tip I can offer - get outside into the sun and find a few things that you can do when you're in a bad spot to make you feel happy.
Also, try to think of five things to look forward to every day. This will help get over a small comment that brought you down, and it definitely will help get you through the day. Surround yourself with positive people who care about you whenever possible, and tell your friends if things they say get to you - true friends will do their best to keep you happy.
Lastly, think situations through before acting. I always forget to do this when I'm in a spell of depression and end up saying things I regret. If you get angry because of a comment, think through what you are going to say, if anything, and remember that some people don't think before they insult someone or make negative comments. It will get better!
Ever seen a CBT therapist?