Officiating, at its core, is the ability to make quality decisions under stress. The loud environment, the passion of the players, and running up and down the field, all increase your heart rate. In fact, a lacrosse game is a perfect recipe for a heightened stress response.
Commonly known as the fight or flight response, the stress response is your brain priming your body to protect itself. Imagine your hunter-gatherer ancestors. Those that perished, were less ready to sprint away or fight off a predator. The survivors were the ones with the more refined stress response.