I have had the sense of doing something or being somewhere when experiencing it for the first time. It is actually a tad frightening to me. When it happens it seems as if reality has stopped and an alternative reality has taken over. But it doesn't happen often, so, I hardly ever think about it. Experiencing reoccurring dreams and or nightmares is more troubling to me. If I allow myself to become overtired my sleep is always interrupted by nightmares, some repeating and some new. I wish they were as easily ignored as deja vu.