I lie in bed and look in the mirror. The guy in the mirror is lying down. His right is my left, but the top of his head is the top of my head. That ain't it. Floating in space, of course, it all becomes personal.
Human beings are creatures with bilateral symmetry.
Our left sides are mirror images of our right sides. Not so with top and bottom. I think this is why we have local left and right and a shared top and bottom in the mirror, as elsewhere. They have no symmetry at all. Yet tell them to turn left and they shuffle round to the left while their mirror image shuffles round to its right.