Pranayama is a Sanskrit word. It is made up of two words, Pran (meaning life force particularly breath) and Ayama (meaning to draw out or exhale). It is an important part of yoga and meditation.
Pranayama is basically a breathing exercise wherein one learns to control breath to attain higher level of consciousness. Our body has several energy channels. When we breathe, the inhaled air regulates all these channels. The amount and quality of air that we breathe and the way it flows through our energy channels determine our state of mind.
I am sure, all of you must have heard that if you feel very angry, you should take slow and longer breaths and it will help to control the anger. Unknowingly, you end up doing a type of pranayama to control your mind and thus anger.
If you breath deeply with air filling your lungs completely, the air or prana level will be high in your body and its flow will be continuous, smooth and steady. As a result, your mind will remain calm, happy and positive. On the contrary, shallow breathing may fill one with stress, worries, impatience and unnecessary fear.
So, to stay fit and feel calm do pranayama every day.