I Shut Down When I'M Upset

Silence Is My Answer... Whenever I get upset or just not in the mood, I become quiet. I shut people down, I'm in my own little world and I wish no one would bother me. Because if I speak, it would come out rude, impolite or harsh. When I'm upset I keep it to myself, so when someone try to make me open up, I exploded. I know it's bad habit. Usually I just let silence feel the room until I calm down and everything's okay.