忠言逆耳 Honest advice is unpalatable
Explanation
忠言逆耳利于行，意思是正直的劝告虽然听起来不顺耳，但却有利于改正缺点错误。
Honest advice may offend, but it is beneficial; it means that sincere advice, although it sounds unpleasant, is helpful in correcting shortcomings and mistakes.
Origin Story
话说汉高祖刘邦入咸阳后，面对秦宫的富丽堂皇和无数的珍宝，动了安居享乐的心思。这时，他的大将樊哙上前劝谏，说：“如今天下尚未平定，您却贪图享乐，这可不是明智之举啊！”刘邦有些不悦，但张良在一旁提醒他：“忠言逆耳利于行，大王还是听从樊哙的建议吧！”刘邦这才醒悟过来，放弃了安逸享乐，及时整顿军务，最终成就了汉朝的基业。这个故事说明，即使是逆耳之言，只要是出于忠心，并且对自身有益，也应该虚心接受。
It is said that after Emperor Gaozu Liu Bang of Han entered Xianyang, facing the magnificent Qin Palace and countless treasures, he had the idea of settling down and enjoying himself. At this time, his general Fan Kuai stepped forward to advise him, saying: “The world is not yet pacified, but you are indulging in pleasure. This is not a wise move!” Liu Bang was a little unhappy, but Zhang Liang reminded him aside: “Honest advice may offend, but it is beneficial. Your Majesty should follow Fan Kuai's advice!” Liu Bang then realized this, gave up comfort and pleasure, reorganized the military affairs in time, and eventually established the Han Dynasty. This story shows that even if the words are unpleasant, as long as they are sincere and beneficial to oneself, they should be humbly accepted.
Usage
用于劝诫，告诫别人要虚心接受批评和忠告。
It is used to advise and warn others to humbly accept criticism and advice.
Examples
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他说的虽然难听，但句句是忠言逆耳，值得我们认真考虑。
tā shuō de suīrán nán tīng, dàn jù jù shì zhōng yán nì ěr, zhídé wǒmen rènzhēn kǎolǜ
Although what he said was unpleasant, every word was a sincere and unpleasant truth worthy of our careful consideration.
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良药苦口利于病，忠言逆耳利于行，我们要虚心接受批评。
liáng yào kǔ kǒu lì yú bìng, zhōng yán nì ěr lì yú xíng, wǒmen yào xūxīn jiēshòu pīpíng
Good medicine tastes bitter but cures disease; honest advice may offend, but it is beneficial. We should humbly accept criticism.