What to do after completing twilight princess?

I just played and completed zelda twilight princess for the 1st time and i have every item, heart piece, 60 poe souls and sub quest complete and i beat the game and found the ending really sad but what can i do now? i speak to midna and she tells me to go to hyrule castle but i just completed it so im confused on what i can do next, also i have beat the cave of ordeals 2x.