I used to get it really bad... Total cog fog! I'd start talking and forget what I was going to say, forget what the topic of conversation was, lose track of what people were saying to me... Slow to catch on, that sort of thing.

Now it only happens when I've overdone it and I'm too tired. When that happens I just fine a quiet way to excuse myself and sleep in the car! Or whatever is handy at the moment.