I've noticed that the state of mind I'm in seems to affect my chess a lot, especially correspondence chess. Normally, when I play chess I look at all of my possible moves, pick the better ones and then look at all of blacks possible moves to those, and then go deeper into lines I think that are most likely. I seem to have pretty good results with this. However, when I'm upset I seem to play way too quickly. I seem to lose my patience, and play at blitz speed. This obviously has a negative effect on my game. I end up moving entirely based on intuition. In general, I'd say 80% of the time when there is only one move I pick intuitively I end up agreeing with that move after further analysis, however the other 20% kills me. For the past few days, I've been dealing with certain problems which I'd rather not discuss, however I have definitely seen a negative impact on my game.
I was just wondering if there have been any studies on how people's mind-state's effect their game.