I have been debating whether or not I should keep a 'mood log' of some sort. Recently I've been exceedingly moody, really inexcusably so. Last night I was alternately hopelessly depressed and raging. In the morning I was relatively happy. After going to see Stereo Total I was pretty wiped out, and back to irrationally depressed from Saturday night to Sunday night.
So the advantages would be that I know just how often I'm pissed off and maybe I can structure things so that I stay happier for longer. The disadvantages would be perhaps discovering that I'm just depressed or angry 90% of the time. Maybe I'll institute it later.