This breathing exercise is best practiced in the evening or at night as it is associated with the cooling energy of the moon (Chandra) and can help you relax and stay calm.
Steps:
Find a comfortable seated position, either on the floor or in a chair, with your spine upright and your shoulders relaxed. Rest your left hand on your left knee in Jnana Mudra ( index finger and thumb touching ).
Gently close your right nostril with your right thumb. Your other fingers can rest lightly on your forehead or between your eyebrows.
Close your eyes and take a deep breath in through your left nostril, focusing on the coolness of the breath as it enters your body. Inhale slowly and deeply, filling your lungs completely.
After inhaling, close your left nostril with your ring finger, keeping your right nostril closed with your thumb. Hold the breath for a comfortable duration, but not to the point of strain. This retention is optional and can be omitted if uncomfortable.
Release your right nostril and exhale slowly and completely through your right nostril, focusing on the warmth of the breath as it leaves your body. Try to make the exhalation longer than the inhalation.
Continue this cycle of inhalation through the left nostril, retention (if comfortable), and exhalation through the right nostril for several breaths, maintaining a smooth and steady rhythm.
To conclude the practice, release your left hand and breathe normally through both nostrils for a few breaths, observing any changes in your body and mind.