I don't really show it. I might occassionally snap at people or give them the evil eyes but generally I just get on with it. Worst comes to worst I might vent at a friend.

If I'm having a bad day because I'm upset with people, I do something that might sound really loony. I'm not afraid of confronting people, but no one wants to do that and create problems all the time. So, if I'm really mad or sad because of what someone has done, I'll go off by myself and just have a conversation as if they were there. Generally, it's people I know well enough to know how they'll respond, and so I just tell "them" everything I would want to say to them. I'm able to get those things off of my chest. And, on the plus side, if I have to later confront them, I usually have it well in my head what I want to say.
I do that too, I end up having arguments with myself. All under my breath of course. I did it all the time when I lived with my mother - we really didn't get along.