CALM YOUR NERVES INSTANTLY

You can soothe your nerves using a simple technique called "The Diving Reflex"

What actually is the diving reflex?

The mammalian diving reflex is a reflex in mammals which optimizes respiration to allow staying underwater for extended periods of time. It is exhibited strongly in aquatic mammals (seals, otters, dolphins, etc.), but exists in weaker versions in other mammals, including humans.

In other words, when your body comes in contact with cold water, it automatically responses with:

• Decrease in heart rate by 10 to 25 percent (depending on the coldness)
• Decrease in blood pressure.
• Decrease in other symptoms of stress.
• Purpose of this reflex: The diving reflex is the body's physiological response to submersion in cold water and includes selectively shutting down parts of the body in order to conserve energy for survival.

If you submerge your left arm in ice cold water, you'll experience a reboot in your heart. 

So How can you use the Diving Response?
If you are going to perform e.g. at a competition or at a business event, activating the diving reflex can help you relax. The diving reflex is activated by breath holds and by facial contact with cold water. If you cover your face, especially the forehead and the area around the nose (area of the trigeminal nerve) with a cold wet towel, the diving reflex will be activated. Because the diving reflex innervates the vagus nerve your pulse will drop and your body will relax. In this way you can quickly calm your nerves before a performance.
The maximum response (the braycardia effect) that is, highest reduction in heart rate and blood pressure, can be observed by holding your breath while submerging your face under cold water.

This also a well known ancient Indian technique to reduce stress and tensions

Source : Wikipedia