My husband and I go to a movie. It is a solidly well done movie, a serious movie, with a complicated plot, a sophisticated sound track, and many high priced actors. It is a movie we will soon forget we saw and will most likely check out of the library in five or so years, recalling people saying it was a good movie. And we will watch it and remember, soon into the movie, that yes, we did already see it. And some scenes will be vaguely familiar as they unfold but neither of us will be able to recall anything about the upcoming scenes, and so we will continue to watch, a movie that will prove itself to be once again solidly well done, that we will soon forget we saw for a second time and in another five or so years, on a night that we are bored and looking for an interesting movie, will pick it up and say, "Did we see this? It's supposed to be good."
I get an idea and begin to write. As I write, I get the feeling that I have written these very same words before. So I stop writing and begin to hunt for the thing I believe I have already written. I never find it. Or I do find it and discover that while it might be similar, it is incomplete, or lackluster, or both. So I continue to write what I was writing when I had the feeling that I had written it before. Or I don't and forget about it, until months later, when I am writing something and get the feeling that I have written the very same words before and stop to search for the thing I believe I've already written, only to find the thing I started but abandoned because it seemed I had written it before. Or I don't find it, and continue to write the thing that feels like I have already written it before, thinking I am mistaken, even though I'm not.