Answer:
No matter how little or how much you use me, you change me every month.
Many hear me, but no one sees me, and I only speak when spoken to
Kills the bad ones and the sad ones. Tightens to fit, so one size fits.
A dagger thrust at my own heart, dictates the way I'm swayed. Left I stand, and right I yield, to the twisting of the blade.
What has 4 eyes but can’t see?
What is so fragile that saying its name breaks it?
Difficult
Difficult
Animal
Easy
Food
Funny
Kids
Logic
What am I?