A figure of speech to illustrate the irreversibility of an action

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.

Solution 1:

"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)

Solution 2:

You can't unscramble an egg, dictionary.com

Some processes are irreversible

This, and almost any answer, will be a variant on the Second Law of Thermodynamics. See Hmolpedia for entropy, putting eggs back together and Boltzman models.

In thermodynamics, you can’t unscramble an egg or a "broken egg can't unite back into a whole egg" are oft-used layperson’s descriptions of the either entropy, the second law of thermodynamics, or the arrow of time.

Solution 3:

I like the idiom set in stone. It means an action or event is rigidly unchangeable, and it has a strong connotation. See The Free Dictionary.

Usage:

I can't change my appointment to attend the ball game. It's set in stone.

Solution 4:

You cannot turn back the clock.

Return to the past or to a previous way of doing things: we can’t turn the clock back—what’s happened has happened - ODO

This relates to the desire to go back to a point in time to 'undo' the speech.