Just remember that its a free country, however realise that if you want to go then you are stopping yourself from a great time. If you honestly don't want to go somewhere then say so. The hardest part is knowing that you feel like youve let the person down who has invited you wherever.
Also remember that you can chose the people you go out withm you dont have to be stuck with a group of friends just because you hung around with them at high school. I have found that people i knew in high school, i dont particularly want to hang out with them because we grew apart over time and i don't like their style of turning up at my house and demanding i go somewhere with them, they do it to me all the time. Im busy working and they come over and give me the guilt trip for saying no, and judge me in harsh ways.
I have some new friends who respect if i say no and just leave it, they dont apply pressure on my or try to inflict guilt upon me. these people i get along with better because there is an element of respect. I feel like i need to discard my high old school friends but i dont know how to approach the situation, i am to weak to just go up to them and say "I dont want to see you guys anymore".
I feel anxious all the time because they turn up to my house and dont ask me, they just say "Right, we're going to this club, your coming, its all planned out". Jesus, if your going to invite me then ask me, dont tell me, i hate that.