As an athlete, I found I could really relate to the information presented by the Yerkes-Dodson Law. The basics of this law are shown in the figure below that plots performance versus arousal level. The inverted "U" shape of the curve suggests that there is a middle level of arousal that results in the highest performance in both simple and complex tasks.
Recently, we had a girl join our soccer team who had been playing only basketball for the past four years. She was a goalkeeper in high school, but now she was preparing to play in her first college-level soccer game. I talked to her briefly before the game, telling her to be not too high and not too low, and immediately realized that I was regurgitating psychology class information to her. I figured if I could get her to be in a medium state of arousal, she would be most likely to have a good performance out on the field.
As Minnesota residents, I bet most of us remember the 2009 Semi-final of the NFL playoffs. This was the game where the Vikings basically had their tickets to the Super Bowl booked, but then Brett Favre threw a game-changing interception. The Y-D Law can be used to explain this. Brett Favre was likely so highly aroused by the high-pressure situation, that his performance was low. Can anybody think of other situations where we can apply this concept?