A Marine once told a civilian that everyone is programmed to believe their 80% remaining is their 0% remaining, and the courageous work of realizing that limitation is what unlocks the extreme feats that someone so well physically and mentally conditioned can undergo.
I'm not military, don't know anyone military, and have no particular leanings, but I have always been absolutely invigorated by the apparent, quiet force that service members project. It's inspirational even devoid of agenda.