While holding hands, some of you may experience a slight case of instantaneous subatomic annihilation. If this happens to you, back away slowly and do not show panic. When you are once again safely away from yourself, head directly to the Aperture Science Paradox Resolution lab and ask for James. He'll patch up that hole in your universe in a jiffy, and you won't even feel a thing.
Not really, our brain adjusts to weird stimuli pretty quickly. Sitting slightly painfully your body often ignores it until you try to move again and feel the pain then. Also limbs going numb due to blood loss. I once woke up and tried to get up but something heavy was on my left shoulder making it really hard.
It was my left arm, I didn't realize I couldn't feel or move it until I tried to get up, which automatically uses muscles in that arm.