While there are many here that know more than I about technical archery, I think you answered your own question. You have to relax. Chill dude!

When I suffer from the problem I think you have I concentrate on my breathing, visualize each shot beforehand. It may take a full 10 minutes for me to shoot five arrows. I wipe everything from my mind but the pin and the POI. If I cannot do that (and sometimes I cannot) I take a break....sometimes up to two weeks. When I come back everything is better. You can get incredible results when you can get your mind to cooperate.