From Galactic Pot-Healer by Philip K. Dick
“What I am doing,” Glimmung said, “is this. I am attempting to learn how much strength I have. There is no abstract way of determing the limits of one’s force, one’s ability to exert effort; it can only be measured in a way such as this, a task which brings into view the actual, real limitation to my admittedly finite - but great - strength. Failure will tell me as much about myself as will success. Do you see that?”