说好的天长地久说好的白头偕老
[shuō hăo de tiān zhăng dì jiŭ shuō hăo de bái tóu xié lăo]
It refers to unfulfilled promises of eternal love and growing old together. These words are typically used in romantic contexts where lovers make commitments to each other that were ultimately broken, reflecting on the disappointment in love and loyalty.