“"There are three things extremely hard: steel, a diamond, and to know one's ___.": Poor Richard's Almanack” crossword clue

Reveal the answer to see why it works and where this clue has appeared before.SELF is the answer to the New York Times crossword clue “"There are three things extremely hard: steel, a diamond, and to know one's ___.": Poor Richard's Almanack”. It was last seen in the puzzle of March 24, 2026, where it runs at 51 Across and fills 4 squares. It crosses 4 other entries in that grid — those are listed below and are the quickest way to confirm the letters you already have.