In the words of Lloyd Dobler from the film Say Anything: "Why can't you be in a good mood? How hard is it to decide to be in a good mood and be in a good mood once in a while?"

Honestly. Some people are just so adamant to feel bad for themselves that they can't be happy in whatever they do. I know you feel like you're stuck, but lots more people are in far worse situations than yours - I'm not even talking about third world countries - so if you just changed your perspective at least for a little while, you wouldn't be in this depressing funk.

I always admonish myself when I sink into a mood, because I know it's entirely up to me to feel happy. Of course, I'm talking about mood swings, not the sadness that ensues when something bad happens. Mood swings are caused by no reason in particular except the universe hates you, so I try to get it lifted as soon as I realize I'm in a mood. Sometimes I'll let it simmer for a while until I want to slap myself for feeling so much self-pity. It's way too indulgent.

Listen to some Bob Marley or world music; it always makes me feel better.