HA! I totally feel like that sometimes. When I get to a point where I'm feeling actually happy with life... it almost always gets sabotaged by me wondering when on earth it's going to go away this time and get super sad about the fact that it's going to go away. This usually continues until I trigger myself into a depression, because I don't think that I deserve to be happy.

But then I also have sort of an opposite situation too: I'll wake up depressed, I'll go out and have a relatively fine day, but the MOMENT I'm not occupied... the depression floods right back in. But I'm pretty good at pushing it away if I'm doing things.