Yup, right there with you. I'm "underemployed" and have been for quite some time. I keep getting blown off as "overqualified" for the readily-available jobs (those that bother to tell me anything at all) and I'm underqualified for the better-paying ones (since all my work experience is in I.T. - same as the other 40,000 out-of-work geeks around here). What I *have* been able to get has slowed down the monthly financial bleeding to a few hundred a month but it's spotty work at best and I'm still losing cash. We're barely keeping up, much less turning enough of a profit to think about starting a family.
Yeah, I have my down moments.
But, like others have said, it's a matter of perspective. I'm young(ish), I'm healthy, I've got a great - and working - wife who loves me no matter what, I've got a house, health insurance, cash in savings, fantastic credit, intelligence, determination, a sense of humor....
Let it wash over you but keep it in perspective. Maybe you can use it to do a little introspection/soul-searching. Stuff like that gets easily forgotten when things are busy and/or good. Take advantage and make your current funk something useful. Maybe it's time to care about *new* things.
"Accumulate learning by study, understand what you learn by questioning."
Or some shit like that. [:D]