哀莫过于心不死
[āi mò guò yú xīn bù sĭ]
In Chinese culture, 'the greatest sorrow is an unquiet heart.' This indicates a persistent pain due to some unresolved emotional conflicts. It's like saying nothing grieves more than a broken heart which can't be fixed. In other words, it describes the endless distress and agony brought by unrelenting love, desire or other strong emotion.