Please tell what I should do to control my anger and depression?

This is probally the most sappiest thing I've ever said since I'm 14 but there's a girl at my school, and right when Im on the brink of asking her out I see her walking down the hall, twice, with the same guy. The first time I thought they could have been just friends but now I think they might have been going out. That enraged for the rest of the day plus all of the anger I had already have containned and I can't ake it. I am going to explode if I dont find a solution.