When you are healthy both nostrils are constantly working simultaneously while you are breathing through your nose. However, one nostril is always more dominant than the other. Strangely, the dominant nostril switches every two and a half hours!
There is an actual science of nostril breathing called called Swara Yoga. This type of yoga explains that when one nostril is predominant, the other side of the brain is dominant. For example, if your right nostril is dominant, the left side of your brain will be dominant as well.
The right nostril is directly related to the sympathetic part of the brain, the “fight or flight” mechanism. On the other side, the left nostril is directly related with the parasympathetic part of the brain, the “rest and repair” mechanism.
According to this, breathing through the right nostril will make you tap into a more energetic state of mind, and breathing through the left nostril will make you relax and calm down.
In today’s world there is a tendency to use more of the “fight or flight” mechanism. This results in an unbalanced state of mind by creating more stress and lowering our immunologic defenses.
Fortunately, there are different basic breathing sets. Pranayamas will help you to regain balance and will even allow the yogi to tap into elevated states of being.
You should be able to switch nostrils by concentrating on them. The left side is directly related with calmness, and the right nostril with energy. So if you cannot sleep at night, lie down on your right side, apply slight pressure to the right nostril and breathe through the left.
Yogi Bhajan used to teach us that, when having an argument, it would be wise to wait two-and-a-half hours. After the break, return to the initial argument and you will see that your whole mental state has been altered to the other side.