Many thanks to Shamou, JohnPlace, ZHereford, and Gary for their thoughtful replies.
Shamou, I notice your name popping up a lot when I browse threads. You reply like a madman. No social fear there, eh?
The statement/affirmation of self is a common piece of advice. It seems very kitschy, but on your advice I will attempt it. Self-image problems may or may not be the root of the problem (I suspect they're a part... human beings are so wonderfully complex--everything has some effect, however small). Even if they're not, doing this certainly won't hurt and will probably help. Thanks again.
JohnPlace, thank you for sharing your experience. Some of what you wrote was very familiar (occassionally being so wound up you can't sleep). It was interesting to see your experience and how you made progress with generalized anxiety. I don't feel that's the problem (social anxiety is, but it is limited to situations with another person's approval/judgment). It is good to hear that you've dealt with your anxiety and made such progress. I wish you the best of luck, and thank you for your advice.
ZHereford, you're exactly right. I have extreme difficulty stepping outside my comfort zone. It's a life skill that some people seem to catch very quickly. The most amazing people are the ones who are simply never fazed by unfamiliar situations, who respond courageously and naturally, without analyzing or wavering. They don't look foolish, even when they mess up. This is something I need to work on. My self-opinion varies greatly when it comes to intelligence (something you noted). Shamou's advice will probably overlap with yours here to give both a goal (expanding the comfort zone) and a means to that goal (hold firm to a positive self-image in uncomfortable situations).
Gary, I agree there are a mixture of beliefs, and they interact in subtle ways. I will definitely check out the site. Thank you for the links, as well as the audio files. This weekend should provide me with ample time to listen to them.
Time to get to work on myself. Thanks again for all the advice and comments. This is a truly supportive place, and I'm lucky to have found it.