"It's better to burn out, than it is to rust."
From My My, Hey Hey (Out of the Blue). A really great pair of versions of that song (there are two, My My, Hey Hey (Out of the Blue) and Hey Hey, My My (Into the Black), one acoustic and one electric) can be found on the "Live Rust" concert album he did with Crazy Horse. The studio versions are found on "Rust Never Sleeps", another great record.