I vaguely remember reading something that traumatic or “very important” memories...

I vaguely remember reading something that traumatic or “very important” memories never go through the usual process of becoming memories. Instead, when you recall them, your brain physically “relives” it so it is never forgotten. Probably a evolutionary trait to make sure we learn as much as we can from the experience. This is also why you remember those “times you almost died” in slow motion. Your brain goes into a high resolution mode in those cases, which you remember as slow motion, like speeding up a camera and playing it back at normal speed.

Sorry I don’t have any sources, I’m just a casual reader in this space.