The defense minister of the state of Chu noticed that one of his subordinates, an eighty-year-old blacksmith, still maintained masterly craftsmanship despite his age.
He inquired about the reason. The old man replied, "It is because I abide by the rules. I have liked forging waistband hooks ever since I was twenty. I have been concerned about nothing but waistband hooks and never looked carefully at anything else. By doing so, I have had ample time and energy to master my craft. Once I reached this realm, all things became available for my use."