I agree with Pugilistic. This is purely down to the individual. Losing only looks beneficial when a fighter has success coming back from it.

I would STRONGLY bet that most losses result in a career decline.

Mayweather's close shave against Castillo wouldn't have made a jot of difference to him. Even though many believe he lost that fight, I have no doubt whatsoever he believes he won performing badly. So much so that he jumped straight back in with him to prove his point.