I talked to someone about strong emotions and mood swings and she said something helpful she did was just say out loud, even if she was alone, how she was feeling, for instance, "I'm feeling very angry right now."
I decided to try that method, so when I woke up feeling really depressed, I told someone, and she said, "It's probably because we're moving. Don't worry about it." Somehow, this did not make me feel better at all and for the next hour, I could feel the need to lie down and sob building up in me. Since there were movers in the house, I couldn't do it alone in my room, so I got on a bike and headed to the playground where I did end up crying for a bit before a man mowing the lawn interrupted me. It was then that I somehow ended up with a wood chip in my hand and proceeded to stab my arm before I realized what I was doing and biked away as fast as I could.
When I stopped, I had this uncontrollable urge to cut myself and pawed through my bag looking for anything even remotely sharp. I ended up with a library card, but even that didn't draw blood. After about five minutes, I realized I was being very irrational and made myself stop. It's tomorrow now and thankfully, the cuts don't really show at all.
There's no need to comment. I just feel better when I share these things.