입이 방정이지. (Me and my big mouth)

방정 [n] rash act, A statement or behavior that is not prudent or decent but light and thoughtless.

semi-polite: 입이 방정이지요

>> This expression is used when the speaker has already said something and regrets saying it. On the other hand, it can also be used to express disapproval of another person's behavior or words, telling them they have said something unnecessary and that they should have kept their mouth shut. 

>>  Originally, ‘방정’ is an expression that refers to words or actions that are not praiseworthy, extremely light, and disrespectful.

>>In the dialogue, Jeong-ja told Soo-jung to bring someone, but in hindsight, she is regretting telling her to do it.