I'm going to sound like a patronising wanker here, but honestly so much of that stuff just comes with age. As you get older you will start to not give a fuck about things that you used to agonsie over, either just through becoming more self confident or because there will come a time that you just have to NOT care and get on with it.
My whole life I've been the shy, quiet (rude) one. You will be thrown into situations where you just have to deal with people and new things, and you'll realise that even if you say or do something silly, the world will keep turning and tomorrow is another day. No one is thinking about what you have said/done, except you.
Feel the fear and do it anyway, I believe is the phrase