Fighting really does reveal everything to the other guy. It's not just about who can beat up to or who's tougher, it's who bullies who and who goes easy on who. You change from opponent, so it's about how you deal with a challenge and how you deal with a guy who you can handle easily.
A man is not rightly conditioned until he is a happy, healthy, and prosperous being; and happiness, health, and prosperity are the result of a harmonious adjustment of the inner with the outer of the man with his surroundings.