What is the idiom to describe efforts in vain?

Pronunciation fù zhū dō ng liú

Interpretation payment: handover; Zhu: Right. Throw it in running water and wash it away. Metaphor hopes failed, grades lost, all previous efforts were wasted, as if washed away by running water.

The source of Tang Gaoshi's poem "Feng Qiu Left" is: "If it is noisy, the south mu of land will cost a lot of money."

For example, the manuscript of Clear Water Pool from Zhen to Bing Yin is ~, so the outline is recorded here. (Huang Qingjun slaughtered "The Legend of the Golden Pot with Seven Inks of Yuanyang Seal")

Used as predicate and attribute; Metaphor hope, go down the drain.

Let me give you an example.

Listening to the sound of rushing to collect the test paper, he walked out of the examination room. The word is obviously familiar, but I just can't remember it. Have more than ten years' efforts been wasted like this? No, tears can flow unwillingly. He looked up blankly and met a pair of expectant eyes outside the iron gate. His eyes are firm ...