There are limitations to how far the human body can work itself. In other cycling arenas, some people take dope to get beyond that but even then, sooner or later, you're going to hit a new set of limitations, doesn't matter which way you turn, and when you hit them face to face, I can only imagine, it's a profound experience and a difficult place to be.
Wishing him well - cycling or no cycling, I really don't care, as long as he puts his well-being first.