The hours still work. The discipline still works. The results start to slip anyway. One leader ran companies for twenty years and never went for a run, until the first way stopped working. What actually changes when the old way of operating runs out?

You checked the numbers three times. Not because they changed. Because a decision that used to take minutes suddenly needed to be right twice.

He had made quarterly forecasts for eleven years. Then last October he started second-guessing every number. Rerunning analysis that looked right the first time. He told me he was losing his edge. He was not losing his edge. His nervous system had changed the operating conditions for his brain. And nobody had told him.