I used to sometimes wake up with my heart POUNDING, totally frozen, I don't know whether by fear or lingering muscular lockdown or both. During one (more fanciful/lingering dreamish) incident that comes to mind, I "knew" that I wasn't in my bed, I was...somewhere else, my eyes were closed initially but I got the impression (through my eyelids and then as I managed to inch one eye slightly open) that I was lying on a slab in the middle of a sort of colliseum (sp)/ice hockey rink (in terms of the barrier in front of the seats) place, with things (robes and glinting faceplates on helmets) sitting in the seats (only the slab was actually lit, the seats were in deep shadow) and at least one standing near the slab facing my back. I "knew" that I had to stay still to make them think I was still unconscious, there was a sense that I knew what they'd do if they discovered I was awake, but I actually didn't know/I can't remember now what it was that would happen. Eventually, I slowly calmed down and decided to roll over as quickly as I could to confront the thing standing on the other side of the slab, I did, and nothing was on the other side of my bed. It was like one of those edits you see on tv, I moved and at the end of the movement I was in my room again, as I had been all along, of course, but perceptually speaking.
Freaky or what 
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We do not experience fear, but we understand how it affects you-Legion