Two idioms that sound similar and are often played with for punning effect are peace of mind and to give someone a piece of one’s mind.
peace: Freedom from anxiety, disturbance (emotional, mental, or spiritual), or inner conflict; calm, tranquillity.
The expression peace of mind belongs to a category of phrases that place the feeling of peace within a specific organ or faculty:
peace of heart
peace of soul
peace of conscience
One might seek peace of mind through prayer or meditation. Self-help books, religions, and various philosophies promise it:
Nine Ways to Find Peace of Mind
The peace of mind Jesus offers is not of this world
Islam teaches that in order to achieve true peace of mind… one must submit
I …found great peace of mind in doing what Hinduism exhorts me to do
Then there’s the expression to give someone a piece of one’s mind. It means to chide, to tell someone off, to tell someone how the cow ate the cabbage, to tell someone exactly what you think, in no uncertain terms:
When she saw the lipstick stain on his collar, she gave him a piece of her mind.
The third time the wheel fell off, he gave the mechanic a piece of his mind.
As with so many other common expressions, peace of mind is often altered for commercial purposes or efforts at punning.
I understand calling an opinion blog “Piece of Mind.” I suppose Iron Maiden had a reason for calling an album “Piece of Mind.” And a book store called Piece of Mind makes a kind of sense.
Why you’d name a tobacco brand “Piece of Mind” escapes me. And to call a program for sufferers of Alzheimer’s Disease strikes me as a bit tasteless:
The Piece of Mind program engages individuals in the early to middle-stages of Alzheimer’s through interactive tours and art-making experiences.
Then there is the out and out unintended substitution of piece for peace, as in this headline at EzineArticles:
Buying A Personal Safe For Piece Of Mind And Security
and in this book review of I, Rhoda Manning, Go Hunting with My Daddy & Other Stories:
Gilchrist’s short stories are indeed therapeutic. They tell real stories about real people searching-for love, for happiness, for piece of mind…