Meaning:

Show emotions or feelings openly.

If you wear your heart on your sleeve, you openly express your feelings or emotions to others.

Example: A: How did the interview go? Did he tell you what problems he has?
B: No, it was very difficult to make him open his heart and tell me his true feelings.
He's not a kind of guy who wears his heart on his sleeve.

Be careful when you talk to her. Never wear your heart on your sleeve.

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