Life is supposed to be full of these ups and downs. It's all about how you look at things. If you can take things in a humorous manner, then you've got a great life ahead... you'll be laughing to your grave. If on the other hand, you choose a very pessimistic view, you won't be able to look at the better things that do happen to you, you may even miss a couple chances at that.

And being an introvert is perfectly OK. The only thing you may be apprehensive about is what others around you would think of that. Thing is, why waste your energy on them when they can't even understand what a person has to go through, the things that make them an introvert in the first place?

Just do the things that make you feel better. Volunteering like aaron suggested, does actually help. I've tried it, several times. Just find yourself something which makes you feel better.