Mental toughness is often misunderstood as being fearless, unemotional, or endlessly motivated. But according to David Goggins, true mental toughness has little to do with feeling strong all the time.

David Goggins' book cover for 'Can't Hurt Me' David Goggins is a retired Navy SEAL, ultramarathon runner, ultra-distance cyclist, triathlete, public speaker and published author. Goggins has long been ...