太阳不懂月旳悲白天不懂夜旳黑
[tài yáng bù dŏng yuè dì bēi bái tiān bù dŏng yè dì hēi]
This username expresses the sentiment that the sun and day, symbolizing optimism and brightness, can't understand the sorrow and darkness associated with the moon and night. It reflects an understanding of different aspects of human emotions that can't always be appreciated or understood by their opposite forces.