Well, I still want to try that - have yet to do so.
My best experience in this department is playing FPS games on a team on a league on the internet.
Not shooting for blood or money - only for pride, but I remember when I started that I was such and such good in casual play or in practice, but when the game started and the adrenaline hit (funny how a computer game can trigger that ancient response...) I would throw my shots, I would trip up, I would forget my orders, etc.
Others did this too.
After a time, this went away, although never completely.
When I felt confident, I could channel it into an edge. When I felt outgunned, I had to fight not to let it mess with my head.
So much of a conflict is mental.
You should study some of Boyds ideas on OODA loops - its really a very simple model for what happens in competition.
http://www.belisarius.com
http://www.belisarius.com/theory_of_mc.htm
Funny - it was just a game, but it taught me so much about myself, about conflict, strategy, teamwork, leadership and so much more....