Me too. This so perfectly describes how I feel in social situations, and it's nice to hear somebody say "It's Ok! It's society that's screwed up, not you."
I'm an introvert but I also understand it goes both ways. Some of my extroverted friends may need me to swing the pendulum more their way as well. It may be uncomfortable and draining for me to be that outgoing or engaged, but I think back to the situations in which I made a conscious effort to do so -- I seem to have grown a little bit each time I did.
In case anyone wants to go more in-depth into the inner workings of an introvert, I highly recommend the book "Introvert Power" by Laurie Helgoe. The article sums up most of the basic points pretty nicely though.
http://news.ycombinator.com/item?id=561311