웃는 얼굴에 침 못 뱉는다고 · 웃는 얼굴에 침 뱉으랴
it's hard to be harsh with someone who is friendly (lit. you can't spit on a smiling face)
Example
웃는 얼굴에 침 못 뱉는다고, 웃으면서 사과하니까 화를 낼 수가 없었어요.
You can't spit on a smiling face: he apologized with a smile, so I couldn't get angry.
Word parts
Literally 'you can't spit (침을 뱉다) on a face that is smiling at you'.
Good to know
Pronounced [운는 얼구레 침 몯 밴는다]. Advice that a smile and good manners soften anger, e.g. when facing an upset customer. Also quoted as 웃는 얼굴에 침 뱉으랴.