새옹지마
塞翁之馬 · the old frontiersman's horse
Luck turns unpredictably — bad can become good and back again.
When to useComforting someone after a setback.
Examples
그때 떨어진 게 오히려 잘된 일이었어. 인생은 새옹지마야.
Failing back then turned out to be a good thing. Life's like that.