My brain goes back and forth regularly between being incredibly potent and nearly useless.
I can carry on three different thought chains concurrently, all individually analyzed and unrelated. I can write one thing while reading another and speaking a third and I can listen to two or three different people talking to me at the same time and answer each of their questions, though usually out of order. I can do a task in one hand that is unrelated to the task I am working on in the other hand at the same time and not screw either of them up.
If I deleted what I just wrote I could tell you what I was trying to say, but I couldnt tell you what more than a few of the words in a row were together. I can't remember a conversation I had minutes ago word for word. I can stand up from a chair intent upon a certain goal, and within seconds have no idea what I was on my way to do. I cannot read without going off on at least one or two unrelated tangents and losing all comprehension of the words I am reading. I have had to re-read what I have written so far at least 10 times now because I keep losing my train of thought and having to kick-start it by figuring out what Ive already written.