It seems, after reading WP and testing many different approaches (basically experimenting), I am actually becoming more successful socially... I've become more assertive and carefree, and as a result my social anxiety and second-guessing myself has significantly decreased. I still (often) find myself in confusing situations, and my shutdowns still occur regularly, but in general things have improved a bit all around.
So my advice to any one of you - leave your comfort zone. Try different things, experiment with people. You can even make it into a single-player game if you want, even earning social experience points!
Moreover, stop caring what people think. I love this quote that my counselor told me: "What you think of me is none of my business."