what's done is done
There's no use worrying or stressing about something that has already happened or come to pass. I know this isn't the outcome we wanted, but what's done is done, so let's just try to make the most of a bad situation. I'm really disappointed in what you did, but what's done is done—let's just forget about it now.
What's done is done.
Prov. It is final and in the past. It's too late to change it now. What's done is done. What's done is done. The past cannot be altered.
what's done is done
There is no changing something; it's finished or final. For example, I forgot to include my dividend income in my tax return but what's done is done-I've already mailed the form . This expression uses done in the sense of "ended" or "settled," a usage dating from the first half of the 1400s.