It's easier said than done, but you have to try really hard.

Don't think about it. You have to train yourself not to think about it. The more you train, the better you get at it and the more it goes away. (This is what therapists call Cognitive Behavioral Therapy, which is just a fancy term for something fairly simple).

Keep busy. Exercise. Takes up time and is good for you anyway. Focus on things that will benefit you, like getting in school, doing homework, eating healthy.

Hobbies can also help.

Avoid things that bring you down. For a lot of people, the "things" that bring them down, are actually other people. Cut toxic people out of your life who bring you down, if possible.

Procrastination can make depression worse, so if you're avoiding doing something, then get to it. After you've done it, you'll feel good about accomplishing it too.

Remember that suicide is a permanent solution to a temporary problem, so just don't.

I too sometimes get crazy depressed and angry moods. To deal with the things that piss me off i normally A) think of how my life is better then theirs (the asshole making me feel like shit) and realize that they must be a real low life to take time outa their day just to tell me their stupid garbage, or B) come play css, mute everyone, and rock out to some music, it always helps that way you can not only safely take out the rage and anger without it being detrimental to anyone, but you can relax and unwind with no hassles in the end. Idk if it works for everyone, but ik that knowing youre your not alone with issues does help by itself