Sài wēng shī mǎ
Translation: An old frontiersman loses his horse.
Meaning: A bad incident may be a blessing in disguise or vice versa.
This proverb stems from a story used to support an argument in the Chinese philosophical classic Huainanzi, attributed to a legendary author named Liu An (179 bce–122 bce). The proverb is the first half of a sentence, which in full says, “塞翁失马，安知非福” sài wēng shī mǎ, ān zhī fēi fú, literally meaning, “Who knows, it may not be a bad thing for the old man at the strategic region to lose his horse.”