What do you do when you feel miserable?

Lately I've been feeling really hopeless and miserable. From being a sweet and easy going person that was never bothered by much, I have become a very bitter, caustic person and I have started hurting people that I really care about. Today I had an argument with my mother which turned into me being so rude and disrespectful that I feel like shit now. She's the best person I know and even though she forgave me instantly, I know I've hurt her real bad today. I'm just so disgusted with myself and I just feel so miserable.