"Think of your true physical limits as an athlete as a wall that lies at the end of a bed of hot coals. Those hot coals represent the purely psychological feeling of suffering that you experience in walking barefoot over them toward the wall of your physical limits in a race such as Ironman. There is not an athlete on earth who has a suffering tolerance so great that he can walk all the way to the wall. Everyone jumps off the coals at some point. But some athletes can stand the pain longer than others, and every athlete can find ways to stand the pain longer than ever before, and thereby reach closer to that wall and achieve a breakthrough performance"
Matt Fitzgerald - Lessons Of Iron War: Fatigue Is Voluntary