You get ONE life (unless of course you are a feline), one chance to do anything and everything you want. Do not let something like this control your decisions or ruin experiences for you. The same goes for people. Don’t let people ruin things for you, or control your behaviours or your life choices. 
It’s YOUR life. Share it with others but don’t let anyone, or anything take over the control you have.
Say YES. Make it your mission, to do things you’d never normally do, go places you’d never normally go, meet people you’d never normally meet. How can you make memories, and take new paths in life if you turn everything down?
Taking the quote in the song in THIS blog post “Do one thing everyday that scares you”. I probably wouldn’t take this too literally if you have severe anxiety, but apply it to making decisions every once in a while to begin with. So what if it scares you? Think about how you’ll feel when you accomplish it, think about the opportunities it could bring you. Think how happy it could make you!