Your comfort zone is anyplace or situation you feel comfortable in. So long as you remain in your comfort zone, you are not growing as a person. Now you don't have to suffer from social anxiety to have a comfort zone, many people have comfort zones they stay in even without this disorder.
I personally try to challenge my comfort zone on a regular basis as every time I manage to get out of it, I know I am growing. Most of the time this will not feel good when you first begin to do it, but the more you do, the better the results you achieve become.
Say now you are not comfortable walking into a crowded room, set yourself the challenge to find a crowded area and to walk through it and to keep as calm as possible, the moment you have done it once, the easier it becomes to do it again.
The more you are able to do this in various scenarios, the more confident you become and you begin to grow. It is always uncomfortable and threatening in the beginning, but the more you grow the easier it gets.
Well, that's my take on it anyway, so lets all get uncomfortable and grow!