枉费心计 wasted effort
Explanation
指白费心思，没有达到预期的目的。
It means wasted effort, not achieving the expected goal.
Origin Story
从前，有个年轻人，一心想成为武林高手。他听说深山老林里住着一位隐居多年的武林前辈，便不远千里去拜师学艺。他每天刻苦修炼，风雨无阻，从未间断。然而，这位前辈却深居简出，很少露面。年轻人等了三年，仍然没有机会见到前辈，更别说学艺了。最后，他不得不放弃，黯然离开了深山。回首这三年的努力，他意识到自己枉费心计，付出了大量的时间和精力，却一无所获。这让他深刻体会到机会稍纵即逝，盲目努力而不懂得把握时机，只会徒劳无功。
Once upon a time, there was a young man who wanted to become a martial arts master. He heard that an old martial arts master had been living in seclusion in a deep mountain forest for many years, and he traveled far and wide to seek him out and learn from him. He trained hard every day, rain or shine, never stopping. However, this master rarely appeared. The young man waited three years, still without a chance to meet the master, let alone learn martial arts. In the end, he had to give up and sadly left the mountain. Looking back on those three years of effort, he realized he had wasted his efforts, having spent a lot of time and energy, yet gaining nothing. This made him deeply realize that opportunities are fleeting and blind efforts without understanding the timing will only be in vain.
Usage
用于形容付出努力却没有得到回报，或者努力的方向不对，结果是徒劳的。
Used to describe putting in effort without getting a return, or the direction of effort is wrong, resulting in futility.
Examples
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他为这次考试准备了很久，结果却名落孙山，真是枉费心计！
ta wei zhe ci kaoshi zhun bei le hen jiu, jieguo que ming luo sun shan, zhen shi wang fei xin ji!
He prepared for this exam for a long time, but he failed in the end. What a waste of effort!
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为了得到这份工作，他四处奔走，结果却落选了，真是枉费心计。
wei le de dao zhe fen gong zuo, ta si chu ben zou, jieguo que luo xuan le, zhen shi wang fei xin ji
He went to great lengths to get this job, but he was rejected in the end. What a waste of effort!