In 2012, on his third tour of duty, an improvised explosive device left Dan Crenshaw's right eye destroyed and his left blinded. Only through the careful hand of his surgeons, and what doctors called a miracle, did Crenshaw's left eye recover partial vision. And yet, he persevered, completing two more deployments. Why? There are certain stories we tell ourselves about the hardships we face -- we can become paralyzed by adversity or we can adapt and...