This post remind us several moral value. One of them is how to keep our behavior. Our mind and our mouth often different cause we won't want to hurt someone.
I stand in font of cashier
Chashier : What can i help you?
me in my mind loudly: I am sure you can't do it. I ask you, pay all of my stuffs
Me : Ok here you are
That inside voice can be a real jerk sometimes. You're right. We contain the beast.