1.
what's done cannot be undone
Literally 'spilled water does not return to the tray.' A broken relationship or a deed already done cannot be restored.
覆水盆に返らずだ。
What's done is done.
Etymology
From a Chinese story: when the wife who had left a poor scholar asked to return after he rose to high office, he spilled a tray of water and told her to put it back. 返らず is the classical negative of 返る.
Usage
Often used of relationships and of words that cannot be taken back. English 'no use crying over spilled milk' is close, but the Japanese stresses that the damage is permanent.
Similar words
Related Words
Compare:
後悔先に立たず (regret comes too late)