expression
it's no use crying over spilt milk; regret won't fix the past
A proverb meaning that regretting something after it has happened is pointless; one should think carefully beforehand.
試験に落ちてから勉強しても後悔先に立たずだ。
Studying after failing the exam is a case of 'it's no use crying over spilt milk.'
後悔先に立たずというから、行動する前によく考えなさい。
They say regret won't fix the past, so think carefully before you act.