Just recently had the gravel road reworked by my place. The contractor had suffered a motorcycle accident about 8 years ago that left him parallyzed from the waiste down. Unless you saw him in his chair you would not know that he was in this condition. He operates all of his own heavy equipment including bottom scrapers, dozers, backhoe, graders, etc. He also gets his hands dirty doing the maintenance. They had blown an engine on one of his scrapers and he and his employee removed the engine and sent it in for rebuild. His D-7 cat had transmission problems and to my understanding he made the repairs himself at home in his shop.
From my experience, I have found that ividivuals like this are far more driven than many of us. The struggles they have learned to overcome have made them much more resilient.
Bob