For Those Who Thought Luz Should Have Held Onto The Power After She Defeated Belos, Let Me Offer A Passage

For those who thought Luz should have held onto the power after she defeated Belos, let me offer a passage from The Wee Free Men by Terry Pratchet, as young witch Tiffany Aching faces down the Queen of the Elves in a confilict similar to Luz's:

"The secret is not to dream," she whispered. "The secret is to wake up. Waking up is harder. I have woken up and I am real. I know where I come from and where I'm going. You cannot fool me anymore. Or touch me. Or anything that is mine." I'll never be like this again, she thought, as she saw the terror in the Queen's face. I'll never again feel as tall as the sky and as old as the hills and as strong as the sea. I've been given something for a while, and the price of it is that I have to give it back.

And the reward is giving it back, too. No human could live like this.

... One of the biggest differences between Luz and Belos is that she took only what was offered, and returned it to its rightful owner when she no longer needed it.