I completely understand this sentiment. This may be due to my cyclothymic temperament, but even when I'm down I usually still have periods where I feel better. Sometimes I can get more done during those periods to make up for my depressive neglect. And then I wonder, why can't I just do this all the time? Am I just weak?

I think that the special situation (the stress of your interview; the chemistry of my cycling) changed our brain state just enough so that we temporarily can overcome the depression. And then it's -whoosh!-straight back down.