From Su Shi's (
苏轼, Northern Song)
水调歌头·明月几时有, written at Mid-Autumn 1076 for his brother Su Zhe:
人有悲欢离合,月有阴晴圆缺,此事古难全 - 'People know sorrow and joy, parting and reunion; the moon is dark or bright, full or waning - such has been the incompleteness of things since ancient times.' One of the most quoted couplets in all of Chinese literature.