Dan Crenshaw said he noticed dark, blurry spots in his vision, which led him to see a doctor who discovered his retina was detaching.
DAN CRENSHAW: It really is a deeper discussion on mental toughness and mental resilience, derived from my experiences in the SEAL teams and combat. And then research, and psychology, and philosophy, and US history, and a lot of pop culture, too. So it's a, really, multidisciplinary book that was-- it's a fun to read. It's a deeper discussion that you might have-- than you might have expected from a SEAL or a politician.