What book helps Tom Brady weather life's highs and lows?

In a recent radio interview, New England Patriors quarterback Tom Brady mentioned a transformative self-help book that serves as a 'mantra' for his life. Brady says he's been reading the book every year since 2002.

What does Tom Brady turn to to weather the ups and downs of life – from Super Bowl wins and high-profile relationships to crushing losses and the trials of Deflategate – as an adored, and scrutinized, New England Patriots quarterback?

A book.

That's what he said in a radio interview Tuesday morning, when he mentioned a transformative self-help book he's been reading every year since 2002.

The book is "The Four Agreements" by Don Miguel Ruiz, a self-help title first published in 1997 by the shamanic teacher. A New York Times bestseller that's been translated into more than two dozen languages, the book focuses on four life practices to "create love and happiness in your life": Be impeccable with your word, don't take anything personally, don't make assumptions, and always do your best.

"It's a quick read. It's really good," Brady said in his weekly interview with sports radio WEEI. "For me, I guess it hit me at the right time. It was very relevant at that point in my life. I kind of read it once a year, just to reflect and gain a little perspective. It's served me pretty well."

It's taken him through the highs of his career, like the Patriots' 2002 Superbowl victory, around which time he first read the book. 

Perhaps more important, it's also helped him weather the lows, like Deflategate, the football tampering scandal for which Brady was supposed to have been suspended for four games for his alleged part in the controversy.

Although a federal judge recently reversed the suspension, the scandal took a toll on Brady and his image.

"You must have some vengeance in your heart," WEEI host Gerry Callahan said to Brady about the controversy and those who turned on him as a result of it.

"Well, I think there are definitely moments when you're vulnerable to certain things, but I also think; I read a pretty cool book about nine years ago that is kind of a mantra for my life. And one of the mantras in the book is, 'Don't take things personal.' A lot of times it's not about you, it's how others may feel about themselves and not necessarily about me personally, Tom Brady."

As for trials like Deflategate, Brady said "The Four Agreements" has given him perspective.

"You just reflect on those experiences and when they're not positive, you use them as motivation for things that you may try to accomplish going forward. My motivation as a football player, there is a lot of that. There has always been a lot of that. I think you see that in the way that I play. But also you use anything you can for motivation to try to reach a higher level of performance for me."

It's not the first time Brady has mentioned the book. He mentioned it in a 2008 story by Esquire, in which he called it a "very spiritual book. You read it and you just go, Goddamn."

Brady's wife, supermodel Gisele Bundchen, also mentioned it in a 2010 Vogue article.

Since Brady mentioned "The Four Agreements" in Tuesday's interview, the book has skyrocketed to No. 8 on Amazon's bestseller list. "Not bad," the Boston Globe wrote, "for a 1997 book that falls into the category of 'Native American Demographic Studies.'"