To build a folly is essentially to do something a second time, something at an inopportune moment. That something is always the memory of something forgotten, about which we can paradoxically say "There it is again."
Follies were misunderstood, purposeless constructions. They were often only small, extravagant gestures in a garden, easily whisking off the imagination to distant lands, a sort of time capsule built to awaken the memory and induce surprise in passers-by. They marked locations, organized secondary paths in a park, or simply predicted the arrival of better times—a demarcation, a sacred spot, a mysterious trail, a hill whose tragic rocky nature begged for a tower, a party, or the arrival of summer.
“It is demonstrably true that things cannot be other than as they are. For, everything having been made for a purpose, everything is necessarily for the best purpose.” — Professor Pangloss
That’s the primary difference between an axiom like “Curiosity Killed The Cat” and an axiom like “You Are Not Your User. ” The former rings true in common experience. It’s test-able, like striking a tuning fork or dangling a bit of yarn in front of a kitten. The latter is just some stuff that somebody said.
Sometimes, axiomatic sayings like “You Are Not Your User” no longer have a who that’s saying them. They cease being an actual instruction, and instead serve as a kind of identity, to identify the person who’s repeating the axiom as One Of Us.
The technical term for when an axiom devolves into an ID card is shibboleth: a custom, principle, or belief distinguishing a particular class or group of people, especially a long-standing one regarded as outmoded or no longer important.