The Yogis have been saying this for a long time, and what do you know modern science is catching up these days.  Modern scientific studies, to be found here: Breath Could Change Your Emotions, are proving that deep, slow breathing reduces the stress precedes a presentation, concert, performance, event, and mindful, deep, slow breathing reduces chronic anxiety and PTSD.  If you want to work on it, come to a yoga class or Autumnal Equinox Nidra, to breathe and relax!