The Dictionary of Obscure Sorrows chronicles words that don’t exist but should.
Onism “the awareness of how little of the world you’ll experience”
Klexos: “the art of dwelling on the past”
Zenosyne: “the sense that time keeps going faster”
But my #1 favorite is ambedo, which refers to a moment in time that you experience for its own sake, not something that is linked toward another goal or task.
This video does a better job of explaining.