You say that if you hold in your emotions, you end up self harming. So how will showing less emotion help any? You need to talk about it, before things get to this critical point. Talk, and vent, about things that bug you, before it all builds up. If it's a little thing? Complain about it to someone, and you can both laugh it off later. If it's a big thing, you can come here or go to a friend that is willing to listen, and help if you need it.

I'd offer myself, but I've had my own method of coping, which is shutting it all out. So I can't really empathize much, and I can't really understand what you go through the way someone else could.