Maija,
Sam Sheridan first wrote "A Fighter's Heart" which was basically his experiences with several well known teams/coaches and how they prepare thier fighter's for fights including the author's own first MMA fight.
This second is more about the mental aspect of physical challenges, but in this book he reaches out to several other disciplines including ultra-marathon runners, the legendary wrestler Dan Gable (gold medal in the olympics without giving up a point for the whole competition) an art proffessor, and others
covering the will to win, metntal toughness, breaking an opponent's will,and other topics.
There is an entire chapter devoted to Josh Waitzkin covering his chess career, his immersion into the world of tai chi, his approach to learning, and his current passion which is BJJ. The book was a very easy read because of the stories, but covered a lot of interesting information.
Keep safe and train hard/smart, Mark H
I now have Josh's book in my wish list for amazon.