Pranayama

Learn/Practice alternate nostril breathing (Anoloma/Viloma Pranayama) for about 5-10 minutes daily or when you need to be free from stress.

We do not breathe equally through both nostrils. At any time, one nostril is more active than the other. This depends on which side of the brain is active and the logical/emotional state we are in.
Nasal cycles change with day/night/moon-cycles/solstice and seasons.

Being out of alignment with this cycle depletes natural flow of energy in the body and is presumed to be the cause of most chronic diseases.

Pranayama restores the natural cycle. Alternatively meditation clears disturbing thoughts/emotions, which in turn restores natural breathing cycles. Pranayama and meditation work as a package.

Sutra 38 - Alternate Nostril Breathing

Practice Alternate Nostril Breathing. This regulates the flow of 'Prana' in your body and leaves you with lots more energy. This is especially good if you are suffering from pains or chronic fatigue. Start with about 6 cycles and practice it until you can do this for about 15 minutes everyday. Practice it for at least a month and share any noticeable changes to your health with the group. Even if you miss it for a day or two, get back to the practice.

Here is a good video demonstration:

Related: Belly Breathing, Pranayama

Sutra 16 - Belly Breathing

Air is a vital element that is often ignored in many health regimens. Revitalising our body requires a free flow of oxygenated blood and elimination of carbon dioxide. Shallow breathing can leave us fatigues very soon.

Sit in a comfortable posture and breathe deeply a few times. Now place your right hand over your navel and gently press your belly as you breathe out. As you inhale, gently push your belly outward against your hands.

With practice, you will double your lung’s capacity.

Here is a great video on Conscious Breathing from YouTube: