There are memories that you forget, that you leave behind. Memories that after a while become “a thing of the past”.

They are no more relevant, of no interest.
You changed, and they are part of something that doesn’t belong to you.

Ex’s are a great example of that. There is a time when you feel you can’t get past your broken love story, but then you do, and you go forward.
And if you have the chance to notice how much did you forget you realize that this whole thing became part of your past, not your present.

On the other side there are things that linger. I can’t say it differently.
Things that stays with you in the night, like horror movies, things that pull out the worst of you even if you don’t know.
Like broken walls in a house, like creeps in your heart.
The less you have, the better.

If they stays with you, then it’s time for you to think about why you’re letting them.
I have a dear friend who still thinks about a relationship of a long time ago. Too much time to justify this lingering.

He didn’t move on, at least from my perspective, and it’s blocked into a story when he can’t win because he let this feeling stay with him.

Don’t linger. Move.