Sports do not build character. They reveal it.
Did you think that people get a good character by doing sports? It sounds correct, but it is more like the opposite. They do sports because they have a good character.
Think of it this way. Most people never manage to do sports on a regular basis. They might not have the discipline, and the lazy part of their character wins the battle against the one knowing that exercise is good for the body. Have you ever known that running or going for a walk would be the right thing to do, but instead you ended up in front of your TV? It reveals something about your character! And in the same way, it reveals something about the character of those able to “neglect” those temptations, and instead go out for a run.
Some of us are born with a talent for sports, while some are not born like that. But, we are all born with the ability to grow in character and to take the right decisions. And if you get in a habit of making good decisions, it will get easier and easier. And that is what has happened to some of the best athletes out there. It all started with making a good decision, and then keeping it up, even on the tough days!