Here’s an article by Neil Davidson that appeared in The Brooks Bulletin.
It involves the UFC fights and how obvious mental toughness can be. Here’s a quote from the article by UFC president Dana White:
“This kid was so nervous to fight Matt Serra, it was blowing my mind. I think that Georges St. Pierre needs to work on his mental game, because his physical game is second to none. … The only thing I’ve seen, any kink in his armour, is his head.”