This is a basic technique that is used in both Kundalini and Hatha yoga used to calm the mind in order to relieve anxiety and stress.
For a beginner this Kundalini yoga practice is 3 minutes long it comprises of breathing in and out through alternate nostrils. Rebalancing the hemispheres of the brain; by breathing in through the left nostril the brains reset thoughts and emotional processes encouraging new perspectives. Exhaling through the right nostril, the constant rumination and cautions of the brain are calmed and relaxed. This exercise sets a new set of brain functioning establishing emotional and mental balance at times of stress.