It's funny I have an Introverted S.O. and an Introverted good friend. I find that I require way more alone/down time than either of them. It's like they can constantly be around people, but are quite capable of simply "enjoying the scenery". Me on the other hand, I'm all in the mix when I am around others - talking, making sure everyone feels included, cooking, catering to, blah, blah and I CAN'T turn it off. It is absolutely draining if I do too much of it.