I would have to agree to some extent with Art_in_FL. But I would say it's a combination of natural physical/mental toughness, and also a form of 'practice'--really just plain being forced to cope with a relentless change for the worse in reality. I have experience with a large number of people inflicted with one of the most horrific diseases known to humankind. For many, it progressively takes away their mobility and every sensory system they have, while causing untold physical and mental pain in the process. To me, it's unbelievable how many of them continue on. Even though I have faced very serious threats to my own personal survival, I often think to myself when working with one of these folks, "Holy MOG, I would've given up long ago."

Most are, by far, just normal folks who unfortunately fell victim to this condition. I would say that most just have the normal human drive to survive, but I would truly say that their unfortunate circumstance often has crystallized and intensified this drive to superhuman levels. To me, these folks are the REAL Superheroes of the Universe.