The phrase ancient history can dismiss something still happening inside another person.

Calling something ancient history settles the timeline and nothing else. For the person still carrying it, the event has not receded at all, and the phrase can arrive as an instruction to be finished when the finishing is not available. Chronological distance is a poor measure of how live something is.

Before telling someone that something was long ago, consider that the date is the only part you can actually see. Ask how it sits with them now instead. And if you are the one being told to move on, the passage of time is not evidence about you. Old things stay open for reasons that have little to do with the calendar.