天下負心人不識相思字
[tiān xià fù xīn rén bù shì xiāng sī zì]
'Tian Xia Fu Xin Ren Bu Shi Xiang Si Zi', meaning people who have broken hearts do not understand what it's like to miss someone deeply. The term describes someone expressing disdain toward heartless or faithless people who do not comprehend the anguish and melancholic yearning felt by those left behind.