In May 2015 I flew to Mexico for a long weekend with a group of friends to celebrate one member’s birthday. We spent Friday afternoon beside the pool at a resort, playing a board game. Dave Goldberg, one of my closest friends, decided to go to the gym. His wife, Sheryl Sandberg, stayed with the rest of us by the pool and dozed off.

A version of this article appeared in the January–February 2019 issue (pp.35–39) of Harvard Business Review.