The trick to getting over it is to plunge yourself into situations that scare you, with no one there that is familiar (I.e your safe zone) to fall back on. I know a guy who was always very anxious in social situations, and he went to the US on exchange for a semester. He came back so different, his confidence and charisma is so much higher, and he made so many new friends too.
I think it's like facing your fears... Once you've faced the scariest thing there is, you feel like you can do anything so your confidence goes up.
