I know only that what is moral is what you feel good after and what is immoral is what you feel bad after.
~ Ernest Hemingway (July 21, 1899 - July 02, 1961)
You get into serious trouble when - during a heated exchange - the mind starts to ask questions about your behavior prior to the fight. That's why many times we see a fighter doing quite well in the ring, hitting the other guy almost at will and suddenly, after a couple of rounds of failing to put his rival down or out, he starts to think about the wrong things he did during training.
~ Floyd Patterson (January 04, 1935 - )