So yesterday I was trying to figure out why I was in such a bad mood when things were going well? I figured it out, and am surprised I didn't figure it out sooner.
Your physical state can affect your moods, right? Well, over the past few days I've just been feeling sick. As it turns out, I've been hyperglycemic almost constantly (hyperglycemia is high blood sugar, for those who don't know). I still am, but I'm in a better mood now. Despite the headache, stomachache, and dry mouth that accompanies it. I should be fine soon, though.
Anyway, I asked the question, so I thought I'd share the answer.