What's done can not be undone.
木已成舟
(mù yǐ chénɡ zhōu)
A: You look so upset.
你看起来很失落。
(nǐ kàn qǐlái hěn shīluò.)
B:I picked the wrong answer at that exam question.
刚刚那道题我做错了。
(ɡānɡɡānɡ nà dào tí wǒ zuòcuò le.)
A: What's done can not be undone. It is useless to regret it now. Next time be careful.
木已成舟,现在再后悔也没有用了,只能下次注意了。
(mù yǐ chénɡ zhōu,xiànzài zài hòuhuǐ yě méiyǒu yònɡ le,zhǐnénɡ xiàcì zhùyì le.)