water spilled on the ground cannot be recovered; used to describe a situation that has reached a point where it cannot be undone or reversed; no use crying over spilt milk

metaphor for a divorced woman being unable to reunite with her ex-husband, based on historical anecdotes of figures like 姜子牙 jiāng​zǐ​yá or 朱买臣 zhū​mǎi​chén