piece of mind
observing your pet feline scratch furniture while resting securely in the knowledge said feline's front claws have been removed.
Fluffy's scratching the sofa and you're sitting there smiling...that's piece of mind.
give a piece of mind
to inform in a non-formal matter.
Guy 1: Why a long face larry?
Larry: I don't have much time so I'll give a piece of mind to you, my gf cheated on me and I'm just about to kill her.
Guy Everyone: O.O
Larry: I don't have much time so I'll give a piece of mind to you, my gf cheated on me and I'm just about to kill her.
Guy Everyone: O.O
piece of my mind
Punishing/scholding/Beating somebody because of something he did that makes you angry.
guy 1:Hey!That guy is making fun of us!
guy 2:oh, I'll give him a piece of my mind!!
guy 2:oh, I'll give him a piece of my mind!!