Their ability to handle pressure is way beyond mine, I'm not disputing that for a moment. But even with an advanced ability to handle pressure, the situations that major league athletes are placed in create pressures that go way beyond what we can fathom.
Failures in big spots can be catastrophic events for these athletes. When a player or a coach screws up at a moment when the season is on the line, they can become an object of hatred and derision for a long time. Nobody forgives and forgets Grady, or Buckner, or Schiraldi, never.
In the case of Schiraldi, his failure in Game 6 not only made him a villain in Sox history, it may have ruined his career. He seemed like a very promising arm, but I don't think he recovered from that.
Major league athletes can lose the season for their team, and their fans, and they can lose their jobs.
Who knows how many players who had all the physical talents to be major leaguers were defeated by their fear of failure? Psychological yips may have been what did in Daniel Bard, just for one isolated example.