Piece of my mind and peace of mind are both English expressions. Peace of mind refers to a calmness and tranquility. Piece of my mind refers to a frank summary of one’s thoughts. Piece of mind is not an accepted alternative for either phrase. The individual words in each phrase signal its meaning.

Well, because both expressions are correct, they just mean totally different things: The phrase peace of mind describes the mental state of tranquility or protection you enjoy when free from worry. The idiom to give someone a piece of your mind means to angrily express your opinion to someone about something they have done wrong.

In conclusion, "peace of mind" is a recognized phrase that refers to a state of calmness and serenity. On the other hand, "piece of mind" is not a recognized phrase and should not be used. Instead, use "peace of mind" to describe a state of calm and contentment.

The difference between “peace of mind” and “piece of mind” may seem subtle, yet it is significant in communication. “Peace of mind” is the correct phrase to use when referring to a state of calm and tranquility free from anxiety. Misusing it as “piece of mind” may lead to confusion or unintended meanings.

Peace of mind is serenity, quietude, or an absence of mental stress. To give a piece of your mind is to tell someone what you think, usually angrily or self-righteously.