This was toward the end of tour, but I held my horn up for two hours during ensemble rehearsal once. We were having a bad regearsal and the staff didn't have anything constructive to say and it ###### me off. People tried to talk to me to see if something was wrong, etc. Max it out, tough it out, do a couple pushups to work the lactic acid through your muscles, it helps. I played baritone, and euph players have big balls, imo!! Let em hang and just RELAX. I can't stress that enough. Force yourself to relax. When you think of how heavy it is, it becomes heavier!