It could be many things. Like others have mentioned, this can stem from depression. It can also mean you're just very angry with something going on in your life. A specific event or person. Or, it could be a mixture of things. Anxiety (which I have very badly) could factor in this as well. I don't know what you can do, other than talk to a professional. They may have some medication for it (I am not sure of your history or current medications) but the risks may outweigh the reward in that case. As long as it doesn't cause you to be violent towards people or create something hazardous it should be alright. Just try to think of things that make you happy during these episodes.

Hope it gets better for you.