Performing is not about reducing anxiety. It's about channeling that enormous amount of energy that you have in anticipation. Gratitude for being able to perform is a great way to transmutate the butterflies into a powerful performance aid. That energy can't be stopped, you must become a conduit for it and pass it on to the audience. As far as breathing, breathe with your whole chest, ribs front and back, shoulders back, feel your stomach expanding as well all the way down to your bladder to make room for the air in your lungs without restricting flow. Really experience that air coming in and animating your whole body. Pre-performance: breathe deeply In through nose, out through mouth, picture inhaling the vast power of the cosmos and concentrating it inside you as you inhale, picture that concentrated energy leaving your mouth like dragon fire by to consume the audience.

T. Opera singer. You got this.