Imagine a rusty bolt on the garden door, which has been set wrong, or the door has sagged on its hinges since it was put on, and for years the bolt has never been shot efficiently: except by hammering it, or by lifting the door a little, and wriggling it home with effort. Imagine then that the old bolt is unscrewed, rubbed with emery paper, bathed in paraffin, polished with fine sand, generously oiled, and reset by a skilled workman with such nicety that it bolts and unbolts with the pressure of a finger – with the pressure of a feather – almost so that you could blow it open or shut. Can you imagine the feelings of the bolt? They are the feelings of glory which convalescent people have, after a fever. It would look forward to being bolted, yearning for the raptures of its sweet, succesful motion.
For happiness is only a bye-product of function, as light is a bye-product of the electric current running through the wires. If the current cannot run efficiently, the light does not come. That is why nobody finds happiness, who seeks it on its own account. But man must seek to be like the working bolt; like the unimpeded run of electricity; like the convalescent whose eyes, long thwarted in their sockets by headache and fever, so that it was a grievous pain to move them, now flash from side to side with the ease of fishes in clean water. The eyes are working, the current is working, the bolt is working. So the light shines. That is happiness: working well.
T. H. White, The Book of Merlyn