自作聪明 Too clever by half
Explanation
自以为聪明而乱作主张。指过高地估计自己，主观地办事。
To act cleverly without due consideration; to be too clever by half.
Origin Story
从前，有个秀才，自认为才高八斗，学富五车，去参加科举考试。考场上，他看到试卷上的一道题目，心想：这题目太简单了，我闭着眼睛都能答出来！于是他洋洋得意地挥笔疾书，写了一篇长篇大论，洋洋洒洒几千字，自以为一定能高中。然而，结果出来后，他却落榜了。他百思不得其解，去请教一位老秀才。老秀才看完他的考卷后，笑着说：‘你呀，就是太自作聪明了！这道题目的重点在于简洁明了，你写的太长了，反而掩盖了你的才华。’秀才这才恍然大悟，原来自己的自作聪明害了自己。
Once upon a time, there was a scholar who considered himself to be very intelligent and went to take the imperial examination. When he saw one of the questions on the exam paper, he thought to himself: "This question is too easy; I could answer it with my eyes closed!" So, he proudly started writing, composing a long essay of thousands of words, convinced that he would pass. However, when the results came out, he failed. He couldn't understand why, so he went to ask an old scholar for advice. The old scholar read his essay and said with a smile: "You were too clever for your own good! The key to this question was simplicity and clarity. Your long answer hid your talent." The scholar finally realized that his self-importance had been his downfall.
Usage
形容人自以为聪明，实际上却很愚蠢，结果往往适得其反。常用于批评或讽刺。
Used to describe someone who thinks they are clever but are actually foolish, often resulting in the opposite outcome. Often used for criticism or satire.
Examples
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他自作聪明，结果把事情弄得更糟了。
ta zì zuò cōngmíng, jiéguǒ bǎ shìqíng nòng de gèng zāo le.
He was too clever by half, and made things worse.
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不要自作聪明，按照规章制度办事就好。
bú yào zì zuò cōngmíng, àn zhào guīzhāng zhìdù bànshì jiù hǎo。
Don't be too clever; just follow the rules and regulations.