"By controlling the breath (a practice called Pranayama), the yogis found they could alter their state of mind."

In the yogic tradition, the breath is said to carry a person's life force. 

Pranayama is the formal practice of controlling the breath, which is the source of our prana, or vital life force. 

Prana means life force or breath sustaining the body; Ayama translates as "to extend or draw out." Together two mean breath extension or control.

As yogis have known for centuries—and as medical science is beginning to discover—the breath has amazing recuperative powers. By controlling the breath (a practice called Pranayama), the yogis found they could alter their state of mind. 

I've used Pranayama at times when I am really nervous to calm my serves.  At times when I could not meditate because I was too nervous, like before having to speak publically, I practiced Pranayama to calm down.  The deep breaths help calm your entire body and clear your mind. Most times, it allows me to center myself again.

At meditation retreats, we've been told that if we can't do anything else, do Pranayama. 

Deer Seal

Learn this traditional hand seal or gesture used for controlled pranayama with the steps below.

Step by Step

Step 1

Ball your right hand into a fist. Press your index and middle fingers into the mound (or base) of your thumb, so they're held firmly in their curled position. (This mudra is traditionally made with the right hand, but there's no compelling reason why left-handers can't use their dominant hand if they like).

Step 2

Stretch out the ring and pinky fingers. Keep your pinky relatively straight, but curl your ring finger slightly, then press its pad to the pinky's nail. Align the fingertips as best you can; the idea is to "blend" the two fingertips into one.

Step 3

Now bring your hand to your nose. Be sure not to turn your head toward your hand, keep your chin aligned over your sternum. Also be sure to keep your right shoulder level with your left shoulder. Tuck your right elbow in close to the side of your torso without hardening your armpit.

Step 4

For all digital practices, the ring finger/pinky pair will close the left nostril, the thumb the right (unless you're using your left hand). Curl these fingers so that you press the nostrils with their more sensitive tips, not their pads. When you close a nostril, apply just enough pressure to block the opening, not so much that you interfere with the flow of breath through the open nostril.

Step 5

Try this simple practice. Close your right nostril and inhale slowly through your left. Then close the left and open and exhale through the right. Finally inhale through the right, close it, and open and exhale through the left. Repeat 2 or 3 times, then release the mudra and breathe normally for a minute.

The steps for Deer Seal are from the Yoga Journal

For more information on why breathing works and other breathing techniques, read Breathing - Why this works from the Yoga Journal.