A trader's mental construction should direct him to do precisely what other people do not do. — Nassim Nicholas Taleb

The information that a person derived some profit in the past... by itself, is neither meaningful nor relevant. We need to know the size of the population from which he came. If the initial population is 10,000 managers, I would ignore the results.

[B]ecoming more rational, or not feeling the emotions of social slights, is not part of the human race... not with our current biology. There is no solace to be found from reasoning...

A mistake is not something to be determined after the fact, but in the light of the information until that point.