I find when I'm Sick, Tired or Pissed Off, I generally do best at any game I play. When I'm just Happy or Neutral, I do fine, but if I'm Sad or Indifferent, I tend to fail immensely
Unfortunatly, for most situations I have a huge amount of patience, a high immune system, and I don't need much sleep, so I don't get my Power Boosts, if you will.
Example: One day, I came back from work fuming mad. I hopped on Halo 3 online to calm down, and I ended up Sniping to the point where I got two Exterminations (I normally fail epicly with Snipers.) That very same day, my little cousin joined a party, so I started to not care, and I found myself in last place for two matches.