The hallmark of a good sport is someone with courage. Courage comes into play, for instance, by displaying more of nobility and less of shame if you are defeated. It takes courage to be humble and proud in defeat. Being a good sport means recognizing that character is more important than who won. Courage also comes into play in how you handle getting hurt.
Few activities help build courage the way sports do.
It's a skill to be able to control your emotions in difficult circumstances. Anger is the most common emotion that can get you into trouble in any sport. Few activities help build the proper control of our passions the way sports do. Winning gives a boost to your self-esteem, which is valuable and pleasurable. When you win, you are an object of admiration and esteem from others.