What are some downsides to having social anxiety?

I read that the physical symptoms of social phobia (anxiety) vary from one person to the next. When some approach a feared situation, their hands shake. Their hearts beat rapidly. Many experience abdominal distress. Some perspire or blush, or their mouth become dry. Then, too, many finds that it is unpleasant to contemplate sweating, stammering, or trembling in front of others.  “Imagining that others notice their nervousness makes people with social phobias still more anxious,” observes The Harvard Mental Health Letter. “They come to anticipate the resulting awkwardness and poor performance—an expectation that sets off further alarms when they approach feared situations.”