Sometimes I forgot I have already written about something. I just start writing and then later realize I have already made a similar post before. But I have also written about this many times, so no more about it.
Another type of forgotten posts are those topics that I think about writing. But then, for a reason or another forgot to actually write. Sometimes I do write these topics down, but there are those that just pass through my mind and are then forgotten. For these, it would help to be more consistent writing them down as soon as possible so I would at least have them stored somewhere.
There are also posts that I think a lot about writing. So much actually, that sometimes forget that I actually didn't write those. I go through the post in my head so thoroughly I might end up thinking I have already written it. But the truth is I have only written it in my head. Memory is an interesting thing. I could very well remember thinking it through, but can't actually remember whether I actually wrote it down or just thought it through in my head. I don't even know how many posts I think I have written, but have never been published outside of my head.