voluntarily no one decides to stop flying unless they've had a scare.
involuntarily, a medical hiccup can do it.

A pilot at the local airport (who is 85) recently sold his plane. When
I asked him why he said that the sight in one of his eyes was getting
poor, and he didn't think he could pass the medical again.

He also said that he'd been flying 50 years and 5,000 hours, and had
had enough for anyone. No mention of any scare or denial - he just
decided that the time had come to hang it up.

BTW we also have another senior pilot of 86 who just renewed his
medical. Flies his T6 every week (and handles it like the pro he is).

David Johnson