Teg - There was a time in my life when it crossed my mind. I found out that doing something for yourself does help. It could be a hobby, buying something for yourself, doesn't have to be something big. Spending $20 and buying something you like does make you feel better.
Money is always an issue, it was an issue for me at that tiime too. I was in crazy debt. You have to work on it but it does get better.

Apperance help your emotions a lot. IF you look like shit, you feel like shit. Dress up a little bit all the time. Talk to people, not about your life. Don't get personal, just talk about funny crap.

ITS ALWAYS THE PEOPLE, NEVER THE MONEY

Just hook up with friends / family more often. Seriously, I have been through most of your questions that coming to your mind. Its hard to see how its worth it to live. But it is. Religion also helps at times. Tell yourself you will not be depress yourself anymore. I dn't mean just think about it. Say it, say it out loud - so you can hear yourself. Trust me, you feel better.

Work on one thing at a time to make it better. You feel money is the biggest problem? Work on it. See all debts and organize 'em. See how you can cut spending. You know they have these companies that will pay all ur debt off and all u would have is just one low debt.