DICT.TW Dictionary Taiwan

 早知今日何必當初 [ㄗㄠˇ ㄓ ㄐㄧㄣ ㄖˋ ㄏㄜˋ ㄅㄧˋ ㄉㄤ ㄔㄨ; zao3 zhi1 jin1 ri4 he4 bi4 dang1 chu1]
 if I (you, she, he...) had known it would come to this, I (you, she, he...) would not have acted thus (idiom)
 to regret vainly one's past behaviour
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