It can be understood from the following three aspects:
1. The meaning of "poor and lowly couples" refers to the marriage of poor couples. Although they are in love for a while, they will become unhappy as time goes on. They will quarrel over daily necessities, rice, oil and salt, and then face all practical problems with "everything is miserable".
2. To understand it literally, it means that if the family's economic foundation is poor, conflicts between husband and wife will easily arise.
3. According to current parlance, it means that the couple is from a poor family. Even if they try their best to do something, they still have difficulty completing it. This is too sad.