In my case, being unable to do anything when overwhelmed is a HypoKPP thing, but triggered by my SPD. The adrenaline rush from the sensory overwhelm, steals the Potassium from my blood stream. My body, due to the HypoKPP, is incredibly sensitive to any Potassium (K+) changes. Even a 0.2 K+ drop within normal human limits is enough to temporarily paralyze me. An adrenaline rush causes at least a temporary 0.2 K+ drop in my blood serum. I can give a more technical description, but it isn't really relevant to SPD.

I personally need something to go on or I am just not really here, but too much and I shut down from being overwhelmed. One day I will master the ballance. The closest for me is to play board games with friends. It gives me social interraction, but I can look at the board if looking at the other people is too overstimulating. The board game also gives me mental challenges to accomplish when my friends' discussion becomes boring and repetitious. One of my friends brings her crocheting with her while we socialize. It gives her hands something to do while we talk.