You have to keep your three hearts for the entire game, and there's a long list of items that you can't use (for example, no Iron Boots in Water Temple). That means that you
have to pull off difficult glitches and tricks just to advance in the game. Throw that in with the fact that many enemies and bosses kill you in one or two hits, and you'll be playing through the same dungeon many times. I managed to make it to the final boss, but that's as far as my skill was able to take me.