A phrase that has the same meaning as the phrase "It's Water Under the Bridge"....I guess. You should use this after an argument. It means that something happened in the past and can`t be changed. You see, once you squeeze toothpaste out of it's proper tube, the toothpaste cannot go back into the tube. You can get a toothpick and try to push it back into the tube, but I'll be Goddamned if it wont go back, and if some of it does you have, at best, an awful mess.
1. Don't worry about what you said it's toothpaste out of the tube.
2. So what if you lost your v card, it's toothpaste out of the tube.