Failure reveals what optimism was unable to inspect.

Optimism has a blind spot by design: it declines to examine the parts of a plan that would spoil the mood. Those unexamined parts are frequently where the failure comes from, which is why the outcome feels so surprising. What broke was often the thing you were careful not to look at.

Before your next commitment, deliberately look at the piece you least want to think about. Ask what would have to be true for it to work. Optimism survives this better than you expect, and your plan improves.