Every memory we have changes slightly each time we think about it. We add stuff we learn in other places, or we forget stuff that doesn't seem important anymore. Or you think you remember something, like from your childhood, but actually you've just seen so many pictures of it, and your parents have told you about it, so you think you remember it, but you don't. A memory is a process. Instead of a thing. Like a story we tell ourselves that changes from the standpoint we're looking at it.