I also have this problem and it drives me nuts.

I found my old college notebooks on short stories and assignments I wrote.

I couldn't believe that I wrote them. I said omg I was smart what happened?

I'm definately functioning at a different level now and not for the better in so many ways... that being one of them.

It's sad...I don't think in my case I will ever be the way I was nor at the level I once was.