This couplet literally means: don't waste the beautiful time of spring flowers and autumn moon. The most rare thing is to have friends when you are experiencing storms.
The previous sentence "Don't let spring and autumn be a good time" exemplifies the second part of Tao Yuanming's "Second Movement", "Spring and autumn have many good times, and climb high to write new poems";
The last sentence, "It is the hardest for an old friend to come through storms", is a classic of Du Fu's prose Autumn Narration.
Song Xiang, a scholar in the Qing Dynasty, also wrote the same sentence: "Think about the past and think about the future, feel at ease, and don't teach the spring and autumn days."
Extended data:
Sun Xingyan (1753 ~ 18 18), alias Yuan Bo and Yuanru, alias Fang Maoshan, was a famous bibliophile, cataloger, calligrapher and scholar in Qing Dynasty. Yanghu (now Wujin, Jiangsu) was born and moved to Jinling. When he was a teenager, he was good at literature with Yang Fangcan, Hong and others, and Yuan Mei called him "a genius in the world".
In the fifty-second year of Qing Qianlong (1787), he won the second place in palace examination, and served as editor and director of the punishments department of the Hanlin Academy. Qianlong fifty-nine years (1794), promoted to doctor of punishments. Later, he served as a Taoist platform and acting as a provincial judge, honest and clean.
In the sixteenth year of Jiaqing (18 1 1), he claimed to be ill and asked for leave to go back to his hometown. Three years later, I lived in Yangzhou and participated in the school magazine "Quantang Wen". In the twenty-first year of Jiaqing (18 16), he presided over Nanjing Zhongshan Academy. He has given lectures in Taizhou Anding Academy, Shaoxing Academy and Hangzhou Jingjing Society Academy. In order to educate talents. In the 23rd year of Jiaqing (18 18), he died at the age of 66.
He devoted his life to Confucian classics, history, literature, and even a hundred schools of thought contend. Historically, philology, phonology and a hundred schools of thought have all understood its meaning. He is good at epigraphy and seal script, especially at proofreading. The series Ping Jin Ting and Dai Nan Ting are rare books.
He was diligent in writing, accumulated more than 30 years' achievements, collected the achievements of ancient and modern scholars, and published Notes on Ancient and Modern Texts of Shangshu, which marked the peak of the study of ancient classics in China in Qing Dynasty. Therefore, Sun Xingyan became an important figure of the dry armor faction. He is also the author of various anthologies, such as Zhouyi Ji Jie, Records of Visiting Historic Sites Around the World, Inside and Outside the Book Catalogue of Sun Shi, and Records of the Poems of the People of Maoshan.
References:
Baidu Encyclopedia-Sun Xingyan