A maxim that comes to mind lately while watching Rhyu Si-min, Kim Ou-joon, Cho Kuk, Park Eun-jung, and Kim Yong-min

"The mouth is the gate of disaster, and the tongue is a sword that cuts the body (口是禍之門, 舌是斬身刀)"
A single word thrown out carelessly can cause deep wounds to others, and eventually, that misfortune can circle back to become a shackle for oneself. This maxim emphasizes the importance of the wisdom to think once more before speaking and to understand the weight of silence.