What does Yu Qian mean by sunset?

Yu Qian s Poem —— The Original Text of Sunset;

This poem expresses the author's metaphor for the decline of the fate of the imperial court and his resentment at being lonely and helpless and unable to serve the country.

About the author:

Yu Qian (1398 May13-1457 February 16), whose real name is Ting Wei, whose name is Jie An, is a junior official. Han nationality was born in Qiantang County, Hangzhou, Zhejiang Province in the Ming Dynasty. He was highly valued by Emperor Xuanzong of Ming Dynasty because of his active participation in quelling the Zhu rebellion in Hanwang, and served as the governor of Shanxi and Henan in the Ming Dynasty. During the reign of Ming Yingzong, he was imprisoned for offending Wang Zhen, and was later released and became an assistant minister of the Ministry of War. After the Civil War, Yingzong was captured, and Zhu Qiyu, King of Xi, was appointed Minister of War. Yu Qian urged the discussion of moving south, decided to stay in the capital, and invited Wang Tongqun to the throne. Valla soldiers stormed the capital, supervised the war and repelled it. On merit and less protection, the governor's military affairs were finally forced to send envoys to make peace first so that Yingzong could return. In the first year of Tianshun, he was unjustly killed for the crime of "rebellion". Shi Yue Su Zhong. Be disciplined. Yu Qian, Yue Fei and Zhang Huangyan are also known as the "Three Masters of the West Lake".