What's done is done

It usually means something along the line of: the consequence of a situation (which was once within your control), is now out of your control, that is, "there's no changing the past, so learn from it and move on."

One of the first-recorded uses of this phrase was by the character Lady Macbeth in Act 3, Scene 2 of the tragedy play Macbeth (early 17th century), by the English playwright William Shakespeare, who said: "Things without all remedy Should be without regard: what's done, is done"[2] and "Give me your hand. What's done cannot be undone. – To bed, to bed, to bed!"[3]

Shakespeare did not coin the phrase; it is actually a derivative of the early 14th-century French proverb: Mez quant ja est la chose fecte, ne peut pas bien estre desfecte, which is translated into English as "But when a thing is already done, it cannot be undone".[4]

It was first used in the Mahabharata when Vidura tells Dhritarashta when Dhritarashta realises the consequences of his actions.

• List of idioms in the English language