I don't know if this is a mood thing. Ultimately the only thing that gets me truly motivated to write (either poetry or a story) is when I want to read something that doesn't exist. I can force myself to write at other times, but I don't really enjoy the work I do then as much.

For mood, I find that I also enjoy the stuff that I write when I'm tired better, for whatever reason. Usually early in the morning, right before I go to bed.