Answer:
Kills the bad ones and the sad ones. Tightens to fit, so one size fits.
This is needed both for courage and hardcover books.
Always old, sometimes new. Never sad, sometimes blue. Never empty, sometimes full. Never pushes, always pulls.
My life can be measured in hours. I serve by being devoured. Thin, I am quick. Fat, I am slow. Wind is my foe.
What gets closer when you blink?
Do what he says and you'll be fine, don't and you lose the game.