What does "poor couples mourn for nothing" mean?

Origin: Wu Zixu, the word (779-83 1), is the most representative poem of Luoyang (now a native of Luoyang, Henan). The long narrative poem "The Poem of Lianchang Palace" and Bai Juyi's "Song of Eternal Sorrow" are also called, and his mourning poem "Mourning" is three famous poems. The clothes you have worn have been given away, and I can't bear to open your sewing box. Because I miss you, I love girls very much, and many of your dreams, I will burn paper for you. No one knows that the husband and wife will be sad, and many past memories are extremely sad. Pepsi's dissatisfaction with the sadness at the end is the same. Mainly write "Pepsi mourning" after the death of his wife. The poet wrote several things that caused sadness in daily life. People have passed away, but the remains are still there. In order to avoid thinking, he gave away his wife's clothes; Leave my wife's needlework intact and reluctant to open it. The poet wants to seal up his past memories in this negative way, and this practice itself just proves that he can't get rid of his thoughts on his wife. Also, every time I see the servant girl around my wife, it also causes my own sadness, thus giving the servant girl more pity. Everything hurts during the day, and at night I dream of flying over the underworld to find each other. Giving money in a dream seems absurd, but it is touching infatuation. The wife who suffered all her life died, and the husband who is now living a rich life does not forget the old love. What can he do for his wife besides "going back to camp to fast"? So the dream came true, and the dream of sending money to his wife appeared. The last two sentences, from the generality of "this is a sorrow that all mankind must know" to the concreteness of "but not as people who have been poor together know". It is inevitable that couples will die, but it is even more sad for couples who have a hard time with the poor. The last sentence is advanced from the previous one to a higher level, focusing on the grief and indignation that is different from the general one.