I get that sometimes, especially when I am in an unfamiliar place, or a place I don't frequent. Eg, I never have this problem with my bathroom mirror at home, but once recently in the men's room at the movies I had a startled double-take when I saw my reflection.
I also have a minor difficulty with face recognition, in that sometimes I have to think about whose face I am seeing.
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"Some mornings it's just not worth chewing through the leather straps." -- Emo Philips