Somewhere between 1980 and 1985, I checked out a hardback SF anthology from a library. English language, with stories by many different authors. Today the memory of one of those stories popped into my head. I remember nothing about the author or title. But I vaguely remember the general plot, and the surprise twist at the end.
The main character (hereafter called "Protagonist" since I can't recall his name) is a teenager as we first meet him, who turns out to have a rare genius for inventing things. I believe he's your stereotypical farm boy, somewhere in a rural area of the USA. Anyway, Protagonist invents something . . . makes some money . . . uses this to finance other Research & Development projects . . . and ends up making a great deal of money over the next umpteen years. So far, so good!
In his old age, after a long life, Protagonist is dissatisfied by thoughts about what he accomplished, on the one hand, and what opportunities he now sees he missed, on the other. To his way of thinking, the answer is obvious! He uses his inventive genius to build a time machine, and travels back several decades to have a talk with his juvenile self.
We are told the general outline of this long talk. I believe much of this story was written as if a narrator were telling us the story long after the fact, summarizing major events for our benefit, instead of giving us word-for-word accounts of entire conversations. I don't remember exactly what Old Protagonist advised Young Protagonist to do differently, but I do remember that Young Protagonist took this advice to heart to guide his life.
Result: Once again, we get a quick summary of the next several decades of Protagonist's life, as he invents even better things than before, and makes a lot of money (and perhaps accomplished other stuff I can't recall now). Until . . . in his old age, after a long life, Protagonist is dissatisfied by thoughts about what he accomplished, on the one hand, and what opportunities he now sees he missed, on the other. To his way of thinking, the answer is obvious! He uses his inventive genius to build a time machine, and travels back several decades to have a talk with his juvenile self.
The cycle repeats itself again. Young Protagonist listens carefully to his elderly visitor, and subsequently improves upon his past performance (not that he directly remembers the "previous lives," but he does remember the advice he got from that weird old man when he was a teenager) and in some ways does even better than before. But this time around, as he gets old, he begins to regret not just the details of what he did or didn't accomplish, but the basic fact that he has not had enough time to do all the other stuff that he's sure he's still capable of doing . . . if only he had a much longer lifespan to play around with! So he builds a time machine (each time around, he has to invent it all over again from scratch, you understand) and goes back to give his teenage self yet another rousing pep talk on the subject of getting his priorities straight.
This time around, Old Protagonist talks in very lofty terms about the importance of concentrating on discovering the secret of Eternal Life. Once Young Protagonist has that problem licked, he'll have all the time in the world to invent anything else that really needs to be invented for the greater benefit of the human race, and so forth.
After Old Protagonist walks back to his time machine to return to his future timeline, Young Protagonist is left scratching his head and just thinking, "What a weird old coot -- what was he going on about?" (Not an exact quote.) In other words: the implication is that this cycle of endless second-guessing and time-traveling has finally been broken, because Old Protagonist had forgotten how wide the intellectual gap was between his very experienced self and his not-nearly-so-educated juvenile self, after something like 60 or 70 years (or however long it had been). So that Old Protagonist's Important Speech about the quest for eternal life was expressed in such a way that it just went right over Young Protagonist's head instead of inspiring him to direct his thoughts toward a fruitful line of research which he might actually pursue. I got the impression that now Young Protagonist was never going to even come close to inventing a time machine of his own when he became a crotchety old man (although I'm not sure if he would still end up owning any patents on useful inventions).
That was the general plot of the story. I have never run across it again. Does anyone recognize it?