I turned my heart to the bright moon, but the bright moon shone on the ditch.

Falling flowers deliberately follow the running water, and the running water has no heart to love falling flowers.

It means: I treat you kindly, but you are indifferent and ungrateful. My sincere efforts have not been rewarded and respected.

The bright moon here can be compared to both people and things, which implies that I treat you kindly, but you are indifferent and ungrateful. My sincere efforts have not been rewarded and respected.

Extended data:

The Story of Pipa is adapted by Gao Ming from the long-circulating folk opera Zhao Zhennv Cai Erlang. According to the Narrative of Nanci, the original plot of Zhao Zhen's Daughter Cai Erlang was to expose Cai Bozhen's betraying his wife and stopping his wife to remarry once she was successful in official career.

Later, Zhao Zhen's daughter went to Beijing to look for her husband, but Bo Yi was morally bankrupt and trampled on Zhao. As a result, he was punished himself and was violently killed by Lei Zhen. The whole plot is similar to "Wang Kui" and "Zhang Xie's No.1 Scholar", and they all castigate the despicable behavior of feudal scholars who are ungrateful.

However, when Gao Ming adapted Zhao Zhennv into The Story of the Pipa, he wrote Cai Bozhen as a positive figure, praising him as a typical example of loyalty and filial piety, and changed the tragic ending to a happy ending.