Bad Moods

A number of things can get people into a bad mood.
An injustice, a rude remark, hunger, heat, disrepect; like taste in music, it varies from people to people what cues set them off, but the question is: how do you get out of it?

Fresh air, deep breaths, jokes, venting- that's a good one, but sometimes it's not enough.
And a bad mood can ruin important evenings, relationships because they destract from larger pictures and goals. Sometimes people feel justified by their mood and let it rule themselves, others may not even know why but let it continue to destroy their time anyway, and sometimes people feel justified, but realize that its important to not let their mood affect their evening and try and try and try to snap out of it, but can't.

How do you get yourself out of a bad mood? When understanding that it's important not to let it affect your time isn't enough to snap you out of it?