There's an old SF short story set in a future in which ageing has been stopped world-wide by a macguffin device which causes "higher mammals" [sic] to perfectly repair themselves on a 24-hour cycle, including restoration of brains to their previous states. The inhabitants of this world carry chained to their writsts external memory storage cubes emblazoned with instructions to remain calm and to perform the actions that will upload the stored memories.

*googling*

Ah, yes, here it is: "The End of Summer" (1954) by Algis Budrys. It's been a while since I read it, but I remember liking it as a 12-year-old (and no, that doesn't mean I'm now 61). It did manage to infect me with the meme "there's still a law of averages."