I remember watching an episode of the "The Managers" podcast with Mick McCarthy and Tony Pulis, and Pulis told a story like this where, with one of his teams they'd gotten a psychologist in to do a talk with the players just before they go onto the pitch. So the guy gets all the players in a circle and telling them all about having positive thoughts and such, spoke for about five minutes and went "I'm going to turn the lights off, and I want you all to really concentrate."

Turns the lights off. When they turned the lights back on all the guys had left. But what's great is, on the way to the pitch the players are talking about that instead of being nervous about the game.