water under the bridge | water over the dam
Meaning: You can say a problem or an experience is water under the bridge, or water over the dam, if it happened in the past and it no longer affects the present to a degree that is worth worrying about.
- I wish people would stop talking about my problems with the law. It all happened a long time ago and it's water under the bridge as far as I'm concerned.
- Rhonda says her marriage to Mark is water over the dam and it's time to move on with her life.
Sam says some things are water under the bridge and he doesn't want to talk about them, such as