The problem with being manic for months on end is that the initial exuberance and excitement has a way of turning into paranoia and anxiety. I'm not exactly sure how it happens, but it does.
It's weird like that. It's like at first the thoughts move wonderfully, like you're in the flow you get programming, but all the time. Then they move faster, and faster, and faster, and suddenly your brain is more chaos than anything.
But it still beats the depression :)