Golf immortal Arnold Palmer recalls a lesson about overconfidence: It was the final hole of the 1961 Masters tournament, and I had a one-stroke lead and had just hit a very satisfying tee shot. I felt I was in pretty good shape. As I approached my ball, I saw an old friend standing at the edge of the gallery. He motioned me over, stuck out his hand and said, “Congratulations.” I took his hand and shook it, but as soon as I did, I knew I had lost my focus.

On my next two shots, I hit the ball into a sand trop, then put it over the edge of the green. I missed a putt and lost the Masters. You don’t forget a mistake like that; you just learn from it and become determined that you will never do that again. I haven’t in the 30 years since.

Carol Mann, The 19th Hole (Longmeadow), quoted in Reader’s Digest