How come I feel like this?

I don't know why, but this happens every day. There are no exaggerations here. At one point I feel like killing this one person and making their life hell, and then the next I want to hug this person and make sure they have a perfect life (Same person). At one point I feel like I want to cry for no reason, and then the next I find myself laughing hysterically. At one point I feel so tired I want to just fall asleep in cl, and then the next I want to jump all over the place and zip around. You get the point. I don't really know what is going on; can any of you explain this to me?