Source identified1
“Regrets are the natural property of grey hairs; and I enjoy, in common with all other men, at least my share of such inheritance.”
Old Martin treats regret as an almost ordinary inheritance of age: living long enough produces memories of choices, estrangements and missed opportunities that cannot all be revisited without hindsight.
Source note: Martin Chuzzlewit, Chapter X, Project Gutenberg #968. Old Martin Chuzzlewit says this while speaking to Pecksniff. The scene is part of a deliberately strategic performance inside the novel, so the maxim remains attached to the character rather than being flattened into direct Dickens autobiography.