Darkness Visible by William Styron

"...and that is the inability of the psyche to absorb pain beyond predictable limits of time. There is a region in the experience of pain where the certainty of alleviation often permits superhuman endurance. We learn to live with pain in varying degrees daily, or over longer periods of time, and we are more often than not mercifully free of it...except in intractable terminal pain, there is almost always some relief; we look forward to that alleviation...and we embrace this eventual respite as the natural reward we receive for having been, temporarily, such good sports and doughty sufferers..."