Breathing (and breathing correctly) is much more important than merely keeping us alive. Improper breathing can actually cause stress on our bodies and alter our blood chemistry. We all know that taking a couple of good deep breaths can help us to relax, but often we forget to monitor our own breathing and unconsciously fall into bad breathing patterns. Read this short article by a former Apple and Microsoft exec:

http://www.edge.org/q2008/q08_10.html