Help!

Went to face Ganon with one heart and lots of gloom perished hearts. The game doesn’t allow me to travel to the surface to regain my hearts. Ganon kills me in one swoop and I am doomed to repeat this again and again. What can I do? Help!!!

Went to face Ganon with one heart and lots of gloom perished hearts. The game doesn’t allow me to travel to the surface to regain my hearts. Ganon kills me in one swoop and I am doomed to repeat this again and again. What can I do? Help!!!