Cyclic Sighing by Dr Spiegel
Various clients have found this breathing technique to be simple yet very effective:

Dr David Spiegel, is a world-renowned psychologist. He is a leading authority on the clinical use of hypnosis, as was his father before him - Dr Herbert Spiegel.
"Spiegel" is the German for mirror, which somehow seems appropriate to me.  Read more about Dr Spiegel here.