费力不讨好 toil without reward
Explanation
指做事花费力气却得不到好处，甚至适得其反。
It means to put in effort but get no reward, and may even get the opposite result.
Origin Story
从前，有个农夫辛勤耕种，却总是遇到不好的天气，庄稼歉收。他听说城里有个算命先生很灵验，于是千里迢迢去求他指点迷津。算命先生掐指一算，说：“你命里注定要费力不讨好，不如改行。”农夫半信半疑，还是坚持耕种，结果依然颗粒无收，最后不得不放弃农耕，改行做起了小生意，反而赚了不少钱。这个故事说明，有时候，即使再努力，也可能事与愿违，与其费力不讨好，不如另寻出路。
Once upon a time, there was a farmer who worked diligently but always encountered bad weather, resulting in poor harvests. He heard that there was a very effective fortune teller in the city, so he traveled a long distance to seek his guidance. The fortune teller, after some calculation, said, “Your fate is to toil without reward; you should change your profession.” The farmer, half-believing and half-doubting, still persisted in farming, but the result was still a poor harvest. In the end, he had to abandon farming and started a small business, which unexpectedly made him a lot of money. This story illustrates that sometimes, no matter how hard you try, things may not go as planned. Rather than toiling without reward, it's better to seek another path.
Usage
作谓语、宾语、定语；指白费力气，没有效果。
Used as predicate, object, and attributive; means wasted effort, no effect.
Examples
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他帮了邻居那么多忙，到头来却费力不讨好，真是令人惋惜。
tā bāng le línjū nàme duō máng, dào tóu lái què fèi lì bù tǎo hǎo, zhēnshi lìng rén wǎnxī。
He helped his neighbors so much, but in the end it was all for nothing and brought him only trouble. It's a pity.
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这次的项目虽然失败了，但我们尽力了，至少没有费力不讨好。
zhè cì de xiàngmù suīrán shībài le, dàn wǒmen jìnlì le, zhìshǎo méiyǒu fèi lì bù tǎo hǎo。
Although the project failed, we did our best and at least we didn't waste our efforts.