The euphoria attached to Samadhi is beautiful. It is many times addicting too. The student knows his limitations so he could easily get out. Once or twice in this lifetime is enough. To chase it could lead to a painful downfall. He needs to come back so he could share this wondrous spiritual journey.
The subtle body is inherently closed for a significant reason. Once it is made open, the subconscious awakens which in turn emerges our karmas. Hatha Yoga is very easy to practice. However, it produces potent and immediate results to the practitioner. The outcome depends on what is ingrained in the subconscious mind of the student.
Once the nada is heard, slowly pierce through it until a softer sound appears. Focus on this new sound. Then go past the new sound and another one shall emerge. The nada is inside the mind only and the sound is to be heard in the mind only. We cannot create these sounds, they are already there. We have to attune our minds for the nada to manifest.
Finally, we must learn how to breathe through the Union of the Soma and Kundalini. There are actually two places where we could do this practice. One is inside the heart and the other one occurs through the third eye. Feel the inspiring of the breath open the space of the heart and allow it to melt and relax through each exhalation. When we breathe through the heart, the mind and breath are calm and balanced.
In a functional perspective, the goal of pranayama is to refine and make the natural breath healthier, balanced and more efficient. Pranayama purifies the Nadis so that the prana (life force) can freely flow through them, nourishing and recharging our vital organs. Further still, deep and meditative pranayama stills and calms the mind in preparation for the state of Samyama (concentration, meditation and absorption).
The brain and the vital inner organs get most of the energy to sustain their healthy function. This leads to the drying out of our essential fluids, nutrients and tissues, including the Ojas. Yoga is one of the many disciplines which teaches us the various techniques of slowing down the depletion of our vital tissues.