literally carved in the bones and engraved in the heart; used to describe feelings of gratitude or an experience that is etched in one's memory forever

etched into one's heart and bones; used to describe a deep memory or a feeling of gratitude that one will bear in mind forever

Unforgettable; engraved in one's bones and heart; often used to describe deep gratitude or a memory that can never be forgotten.

(idiom) to be eternally grateful; to remember a debt of gratitude for the rest of one's life

deeply felt and unforgettable longing between lovers; deep-seated lovesickness