苦口婆心

earnest and well-meaning advice (idiom); to persuade patiently

heart / mind / intention / center / core / CL:顆|颗[ke1],個|个[ge4]

mouth / classifier for things with mouths (people, domestic animals, cannons, wells etc) / classifier for bites or mouthfuls

bitter / hardship / pain / to suffer / to bring suffering to / painstakingly

grandmother / matron / mother-in-law / (slang) femme (in a lesbian relationship)

lit. bitter taste (cf good medicine tastes bitter 良藥苦口|良药苦口) / fig. earnestly (of warning, advice)

(literary) kindheartedness