Water under the bridge

 Something from the past and is no longer important or worth worrying about - bury the hatchet.

Meaning and Mindset

• Moving On: It is used to show that a past disagreement or problem is no longer important.
• Acceptance: It signals that you have let go of hard feelings and choose not to dwell on the past.

Usage

• We had a big argument last year, but that's all water under the bridge now.
• Don't worry about breaking that vase; it happened months ago and it's water under the bridge.