When the whistle blows you have only a limited amount of time to do what you have to do. You either do it then or you don't do it at all.
Source: A Modest ALL America Who Sits on the Highest Bench, in Sports Illustrated, by Alfred Wright, 10 Dec 1962.
-- Byron R White, (Jun 8 1917-2002), US jurist; He was an associate justice of the U.S. Supreme Court, 1962-93; he also played professional football for one season (1938) with the Pittsburgh Pirates (now Steelers).