What was the downfall of Jason in Greek mythology?

After he found the Golden Fleece, he broke his oath to Medea, a princess taught witchcraft and magic by her aunt Circe, to marry her. He fell out of favor with the gods, namely Hera, and his good looks, friends, and fortune left him. He sat beside the rotting remains of his ship, the Argo, and the prow fell off and hit his head, killing him.