People always ask David Goggins: how did you get so tough? He is the only person to have completed Navy SEAL training (including two Hell Weeks), Air Force tactical air controller training, and U.S. Army Ranger School. Now that he has retired from his military career, he's an ultra-endurance athlete, committing feats of physical and mental resilience like the Badwater 135, which requires participants to run 135 miles in 24 hours in the peak heat of Death Valley. Not that he was always a super soldier: Goggins once weighed 300lbs and was by his own admission lazy and undisciplined. Here, Goggins explains how he transformed himself and won the war in his mind—from positive self-talk and building a 'cookie jar' of resilience, to the 40% rule, here's how you can learn to push past your own mind games. You can follow David on Twitter and Instagram @davidgoggins and Facebook.