Take a deep breath (best lying down or sitting) hold it in, then "pump" out your stomach hold for 1-2 seconds then let it down again, pump it again.. do this 4-5 times and then exhale... This really takes the tension out of your belly area and relaxes you.

When panic sets in: focus on breathing slowly- not too slow, just nomal phase... count in-1-4, out 1-4.. it helps.
Hope this will help