'Prana' is often defined as 'life force energy'. It exists in all living things as the power of life itself. The ancient yogis surmised that breath is the physical correlate to prana. Your breath literally enlivens your body - and after you take your last breath, your life-force energy (prana) leaves you.
A pranayama is a breathing practice designed to expand your life force energy. In later forms of yoga, pranayama is practiced by imposing structures and patterns on the breath, but in Classical yoga, pranayama is a very simple breath awareness practice, as follows:
1) Get into an easy, comfortable position (asana). Relax your effort.
2) Notice, when you are relaxed, that the flow of inhalation and exhalation is suspended
3) Observe the movement patterns of your breath (inhalation, exhalation and pause)
4) Also observe the length and number of breaths and where in your body you sense your breath.
This type of pranayama is a very simple tool for quieting the mind. According to Patanjalai, when the breath moves, thoughts move; when your breath is still; your mind is still. The pauses between your breaths form an uninhabitable environment for mental disturbance. And THIS, good people, is one of ancient YOGA’S GREATEST DISCOVERIES - that thoughts and breath influence one another. When we are upset our breath is quick and shallow. When we are calm our breath is slow and deep. Just as our mental states affect the way we breathe, we can use our breath to affect our mental states.
There is no need to 'restrain' or wrestle with your breath. Your mind can become calm simply by allowing your attention to be absorbed in the task of noticing your breath in stillness and in motion. Here are some ways to engage with your breath on and off your mat.
Intention: "I am a student of my breath"
Pranayama: Patanajali style breath observation (see video for instruction)
Off the Mat: throughout the day, pause and observe how your breath responds to different mental states...when you are relaxed, upset, etc.
Amanda Tripp, Yoga/body nerd and woman of a 1000 opinions