Because I can. Out of 1,205 posts, 14% have been of the mood "amused", 11% have been "tired", 11% have been "happy", 7% have been "annoyed", 6% have been "awake", 4% have been "thoughtful", 2% have been "content", and 1% have been "satisfied", "working", "busy", "shrill", "exhausted", "accomplished", "intrigued", "frustrated", "hungry", "chipper", "giggly", "cheerful", "silly", "horny", "cynical", "curious", "sleepy", "mellow", "geeky", "furious", "disappointed", or "creative". Non-LJ-standard moods have included "petting the cat," "shrill beyond measure," and "coming back to life".
All in all, I think that's not bad. I've done well in keeping my LJ moodiness on the positive side.