It's odd really, sometimes I find myself hand-flapping without really thinking about it when I'm annoyed/frustrated, stressed, overwhelmed, or occasionally excited, but there are moments where it really doesn't seem to help.
After doing so, it can feel as if I'm more on edge than I was at first, which is odd when you consider that hand-flapping is supposed to be a calming thing. Yet, I still do it for some reason. Hmm. I feel more stimulated somehow, which isn't exactly what you want when you are trying to remain calm. 
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Near the spectrum but not on it.