We all love to make fun of some of the more egregious excuses, but the thing is. You absolutely need to be delusional as a fighter.
Knowing you did all the correct preparation, and was the best version of yourself, and still getting beaten, or worse, outclassed, is one of the most demoralising things on the planet.
I actually felt really bad for Marcin Tybura before the Tuivasa fight because he said something to that effect.
Said he really struggled mentally with the Aspinall defeat, as he was the best fighter he'd ever been for that fight, he'd lost weight and was in his career best shape, and he didn't even have a chance to get into the fight. Tom was too fast, too powerful, and too skillful for him to be remotely competitive. He said he had to have a talk with himself about his future because that's the first time he ever lost where he felt he did everything perfect and the other guy was just leagues better than him.