Isaw.
I know your feeling. I have the same thing as you. Here are some things that I hope will ease your mind.
1. You are not the only one. If you have SA, there is probably one other person you know that has it in some form. Some people are just better at hiding their condition than others. Just because they appear at ease, doesn't mean they are necessairly comfortable. Appearances can be decieving.
2. The fact that you avoid someone/something shows that you let others control how you feel. Try this little trick(i'm trying it right now), try to feel good no matter what the situation is(within limited boundaries e.g you obviously wont' feel good if somebody you know dies).
Example
Somebody is screaming/shouting at you for doing something wrong. That's an external influence. Remember, feel good. Tell yourself, it is them that need work! They are the ones upset. Maybe even crack a joke or something, it can lighten up the situation.
E.g You think somebody you work with hates you. So who cares? Feel good. And how do you know they hate you. Do you see where i'm going with this?