I'm looking for a good figure of speech to suggest that something is irreversible.
It would be used in the following context: "I'm sorry, dear, but you said you hate her loud and clear, and there is nothing you can do about it now. _______________________________.
I thought of "once said can't be taken back" or "there are three things that cannot be taken back, the spoken word…" but these are not figures of speech.
Best Answer
"You can't put the toothpaste back in the tube."
This idiom was popularized after the release of the White House tapes in connection with the Watergate Scandal of the early 70's, which contained H.R. Haldeman's conversation with Presidential Counsel John Dean. Haldeman tried to dissuade Dean from testifying to the Senate, saying “Once the toothpaste is out of the tube, it’s going to be very hard to get it back in.”
"The cat's out of the bag."
Letting the cat out of the bag refers to accidentally revealing a secret. It has to do with unscrupulous pig sellers swapping out a bagged piglet for a bagged cat - the deception would be revealed when the buyer came home and "let the cat out of the bag."
Personally I like "You can't unring that bell" as deadrat mentioned above. The phrase refers to the fact that you can't un-hear a bell that has been rung. There's a nice essay about its history here:
Unring the Bell (impossibility of taking back a statement or action)