If I'm getting panicky, I start talking to myself, "You're okay, you're okay, calm down, focus on (something in the car, a building, a sign, other cars, colors, whatever)," and I try to breathe more calmly. I haven't had a full-on panic attack (one that escalates to me running around and screaming for help) in years, but I have had some pretty close calls, including most recently on the Delaware Memorial Bridge.