笑望往日的红尘笑看曾经的你我
[xiào wàng wăng rì de hóng chén xiào kàn céng jīng de nĭ wŏ]
Translating to 'smiling at the mundane life of the past days; smiling at you and me of once', it conveys the sentiment of reminiscing about the past with ease and detachment, often after much has changed.