The fear of losing control is very common with people who have panic disorder. The thing is, say the experts, these are the people who are the least likely to lose control. They are rigid in their self-control. I used to hate driving over really big bridges. I knew I was safe but something in the back of my mind told me I wasn't. I've gotten used to them. My strategy was to drive just slightly under the speed limit, keep both hands on the wheel, and concentrate on keeping exactly in my lane. Soothing music can help.
Since then, I've found that a very simple way to stay calm in a stressful situation is just to breathe slowly, and I'll say more about that.
Basically, therapy for phobias, explained in The Feeling Good Handbook by psychiatrist David Burns, is making a list of situations, ranking them according to how scary you find them, and using that ranked list as your objectives. Imagining a situation can be an objective. Start with something really, really easy.
The thing to remember is never go from objective A to objective B until you feel completely confident with A. Things that give you confidence are experience and slow breathing. There's enormous laboratory and clinical evidence that slow breathing is effective for calming people down quickly.
Two psychiatrists, Brown and Gerbarg, say a 10 or 20 min slow breathing exercise - 5 breaths a min - is good and 20 min twice a day is a therapy for anxiety. The exercise is inhale and exhale gently, 6 seconds each. In the video that's included in this answer with anxiety info, details about how amazing therapeutic breathing is.
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