absence makes the heart grow fonder

all heart

Motivated by positive emotions, especially as productive of exceptionally generous or kind behavior.

be still my heart

An admonition to oneself to calm down when overly excited, especially in terms of romantic attraction.

break someone's heart

To cause a person to feel grief, disappointment, or sadness.

broken heart

A feeling of grief or loss, especially after a failed romantic relationship.

change of heart

A change of one's opinion, belief or decision.

cross my heart

A declaration that the speaker is telling the truth.

cross my heart and hope to die

Added to a promise or a statement to show how serious one was about being honest in what one said

drive a stake through its heart

get rid of, destroy permanently or stop talking about