like misty said.... breathing exercises are always great and yoga ones (yoga in general) i find a great help... it will take a few goes to get into but so does everything?

and doing yoga regularly has help calmed me down and made me more relaxed in general so it kind of helps prevent the attacks in a way i guess you could say... but yes, i would highly recommend yoga and breathing exercises... i close my eyes and take long deep breaths (short to start with till you calm down enough) and focus on the end of my nose, nothing else, try and think of your breath and the tip of our nose.. and believe me in time you can forget about the things around you when you do this

best wishes to you all
molly