Charles Tillman hasn’t become the best cornerback in Chicago Bears history solely due to the physical gifts he possesses. The two-time Pro Bowler credits much of his success to the mental toughness he’s developed thanks to his favorite book, “The Strangest Secret.”

“I always say football is 80 percent mental and 20 percent physical,” Tillman said. “We all have the athleticism to play at this level. But some guys can’t mentally get there. Once I was able to do that, it really helped me out. It helped me hone my skills as far as punching out footballs, getting picks and making plays. From a mental standpoint, I felt like I was ahead of everybody.”

Tillman calls “The Strangest Secret” his “second bible.” He has read the book, which was written by motivational speaker Earl Nightingale (1921-89), every week during the season since 2006. Its basic message is that people with goals succeed because they know where they’re going and that “success is the progressive realization of a worthy ideal.”

“This book has played a pivotal role in my life as far as mental toughness,” Tillman said. “I’ve always thought that mental toughness is the ability to be at your best on command and I learned that from reading this book. This book helps you control your mind and your thoughts.

“You can use this book in religion, the stock market, sports, marriage, writing; whatever it is that you do. You can use this book in every aspect of your life.”

Tillman was astonished the first time that he applied the principles of the book on the football field.

“It was third down and it was probably the 12^th play of the drive,” Tillman said. “I was thinking that I was so tired. But the book says that we become what we think about. So after processing that, I was like, ‘No, get that negative thought out of here. It’s third down and I’m going to make a big play so we can get off the field. If [the receiver] runs a slant, I’m going to pick it off or knock it down,’ and sure enough, I made the play. That was the first time I was like, ‘Wow, I took control of my mind. I took control of my thoughts.’”

Nightingale, the author of the book, was born and raised in California. He enlisted in the Marines at the age of 17 and was one of 12 Marines stationed aboard the USS Arizona to survive the Japanese attack on Pearl Harbor on Dec. 7, 1941.

Nightingale later became a radio star, voicing the character “Sky King” in an adventure series and working at WGN in Chicago in the 1950s. He also purchased a life insurance agency, and recorded a motivational message for his salesmen that later was transformed into “The Strangest Secret.”

Tillman has read the book so many times he says he “pretty much knows it by heart.” He especially enjoys a quote in the book by poet and writer Ralph Waldo Emerson that states “a man is what he thinks about all day long.”

“Your mind is a powerful tool,” Tillman said. “It’s a powerful instrument. Your mind will always return what you plant. If you think: ‘I’m going to get an ‘A’ in this class’ and you study and work hard, you’ll get an ‘A.’” If you think: ‘this class is so hard I’m going to fail,’ you probably will.

“It’s an awesome book, it really is. It’s short and to the point.”

The book is so important to Tillman that he included it in a box of his “favorite things” that fans could order through the Quarterly Company, a subscription service that sends curated gifts in the mail every three months to fans from celebrities.

Later this summer one lucky Quarterly customer who ordered a Tillman box will receive a copy of the book personally annotated by the Bears cornerback.

"I'm happy I'm doing it," Tillman said of including the book among his handpicked items in his Quarterly box. "I wanted to include stuff that means a lot to me and has helped me out in my life. I want to pass the torch and serve somebody else in a good way."