Ben, I used to have severe panic attacks and the only way I could get them to stop was to get up and go for a walk. Next time it happens just try walking and see if it helps. I found that sitting still made it worse....
I would walk around the house or back and forth in my driveway (it was about 200 ft long) or grab a bottle of water and walk around the neighborhood.
I'm glad you are feeling better now.