Long time follower, first time asker
I deeply identify with the second part Nietzsche's aphorism:
'He who fights with monsters should look to it that he himself does not become a monster. And if you gaze long into an abyss, the abyss also gazes into you.'
(Wer mit Ungeheuern kämpft, mag zusehn, dass er nicht dabei zum Ungeheuer wird. Und wenn du lange in einen Abgrund blickst, blickt der Abgrund auch in dich hinein.)
As it relates to a thirst for knowledge that takes you deeper into the rabbit hole (one -- potentially wrong -- interpretation). I found that sometimes unanswerable questions have obsessed me past the point of healthy living, and that to get out of this mindset I had to... just stop gazing
However I do not think this was a novel idea. Are there any examples of this idea in ancient philosophy? Citations & references appreciated
A little more pedantically than you, I would say, regarding that sentence about the abyss, that an adventurous philosopher looks long and hard even where no explanation seems to lie. That's the abyss. Gazing into an abyss feels like a neutral or innocuous desire to know, until you imagine yourself being looked at in the age of looking. The abyss gazes into you, meaning that it spots you looking for something in it. It sees you actively searching for an explanation. In other words, I don't exactly take the sentence as you do, but we're reading it similarly. And I am grateful for your response to it: giving up on gazing when you see you're being gazed at. You can understand Kant's advice to metaphysicians as similar to what you're describing. Stop trying to answer these traditional questions as if they were real questions; learn to diagnose the questions in their unanswerability, down to the human desire to exceed empirical human knowledge. But you wanted to know specifically about ancient philosophers...