夕阳无限好天色已黄昏
[xī yáng wú xiàn hăo tiān sè yĭ huáng hūn]
'Xi yang wu xian hao tian se yi huang hun,' which literally means 'The sunset is so beautiful but twilight has come' expresses the poignant realization that something beautiful is transient as it reflects on time's relentless passage.