There are rather crazy parallels between The Empire Strikes Back and the Book 2 Finale of Avatar: the last Airbender.
The hero goes off in search of a teacher to learn the higher aspects of his special powers. Someone he cares about gets in trouble, and in his meditations he becomes aware of her peril and abandons his training to rescue her.
He does so, but in doing so worries that he might have set his training back irreparably. While in combat with the Emperor’s/Firelord’s trusted and powerful lieutenant/daughter, the hero fails.
The group of heroes gets away to fight another day, but overall the Empire/Fire Nation has won.