Stop and take a deep breath. This will give you a chance to literally catch your breath and realize that you do have control. Take some time to meditate. If you can't, then just repeat a favorite word over and over. The repetition can have a calming effect.
Yoga is a wonderful discipline for getting control over stress.
As a series of exercises, it can range from gentle to strenuous stretches for the more advanced. Everything doesn't have to be doom and gloom. Sometimes it is all in the attitude. The tension can build up and then you'll either inappropriately explode or impair your health, or both. Find safe listeners who you know will be supportive and let you vent.