Mike Matheny, who spent 13 years as a major-league catcher and now manages the St. Louis Cardinals, strongly advocates for living by one’s core principles. A letter he once wrote to a group of parents of a youth baseball team became the basis of the “manifesto.” This forms the basis of his book.
Here's an excerpt from "The Matheny Manifesto":
“Three of my four sons asked to quit baseball at one point or another. Two took a year off and the other came back begging to play again that same season. I shudder to think what would’ve happened if I had made them keep playing no matter what. My fear is, of course, that they could have soured on the game they now love as much as I do and would have given it up for good – because of me. Imagine.
“Naturally, a lot of kids see the yelling as their parents taking their frustration out on them. Regardless how young they are, they know a lack of self-control when they see it.”