Hi,
there is a lot of things in your short question. Most of them are bigger topics and they have been discussed in other threads. Try to search on the forum for yourself.
What I want to say however is about overwhelming feeling you sometimes get. First of all think and talk about it as temporary reaction of your body/mind rather them something permanent. Do not identify yourself with it
Second of all the best way will be to put yourself into this kind of situations (I know it's hard). I think that is most effective and scientific approach. The effect is called Desensitization - take a loot at wikipedia. By experiencing a lot of it, it will be less and less intense.