" Our ancestors could make two kinds of mistakes: (1) thinking there was a tiger in the bushes when there wasn’t one, and (2) thinking there was no tiger in the bushes when there actually was one. The cost of the first mistake was needless anxiety, while the cost of the second one was death. Consequently, we evolved to make the first mistake a thousand times to avoid making the second mistake even once. "

― Rick Hanson , Hardwiring Happiness: The New Brain Science of Contentment, Calm, and Confidence