Fnord wrote:
If you don't realize that you're stimming, then how do you ever know that you stim?

I only became aware of my stims because people told me about them.
WIth my hand/finger stim, a friend pointed it out to me when I was about 16 or 17 and described it as something I do all the time.
With rocking, I was at a work meeting when I was 20 and some workmates of mine mimed my rocking at me .... I can't actually remember how the whole interaction started, but it was one of those situations where people are laughing or having some other reaction and I know it has something to do with me but beyond that I'm lost; So I ask them what's funny or what's going on...or, in this case, nonverbally express bewilderment at them until they realize I don't understand. (I don't think the mimicry or the laughing were mean-spirited -- the mimicry was an explanation, and I guess I must have just looked funny to them.) It took some time, and some additional gesturing/pointing before I figured out they were imitating me and that I had been doing this without noticing.
Now I sometimes become aware of the fact that I'm stimming after I've been doing it for an unknown amount of time. I think I become aware of it when my attention shifts, or when it affects some other movement that I want to do, or when I suddenly have reason to think about my own stimming (e.g. I read a question about stimming on WP).
I'm not sure if I would be aware of it at all if nobody had ever brought it to my attention -- because it wouldn't be something I'd ever have any reason to consciously take notice of. I guess it's a little bit like how most people aren't constantly aware of breathing, in that they only become aware of it if there's some reason to be aware of it.
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"Coming back to where you started is not the same as never leaving." -- Terry Pratchett, A Hat Full of Sky
Love transcends all.