All spiritual aspirants learn methods of transforming energy, but only those in the highest levels of instruction learn the real reasons why and how.

Pranayama is the control of all life-forces. - Sankaracharya

Pranayama is not, as many think, concerned solely with the breath; breath indeed has very little to do with it. Breathing is only one of the many exercises through which we get to the real pranayama. - Vivekananda, Raja Yoga

The aim of Pranayama is the control of Prana. Pranayama begins with the regulation of the breath for having control over the life-currents or inner vital force. In other words, Pranayama is the perfect control of the life-currents through control of breath. Breath is external manifestation of the gross Prana. A correct habit of breathing must be established by the regular practice of Pranayama. [...] There is intimate connection between the mind, Prana and semen. If one controls the seminal energy, the mind and Prana are also controlled. He who has controlled his seminal energy has also controlled his Prana and mind. - Sivananda, The Science of Pranayama

The principal objective of the practice of Pranayama is to obtain the union of solar atoms and lunar atoms, which are found within the seminal system, and consequently to awaken the Kundalini. - Samael Aun Weor, The Yellow Book

No Samadhi is possible without [Kundalini] being awakened. - Sivananda, The Science of Pranayama

The mind of the student is prepared for Dharana, Dhyana, and Samadhi with the practice of Pranayama. [...] The disciple should practice Pranayama ten minutes daily. [...] The disciple should slowly inhale and exhale with his mind very well concentrated in his practice of Pranayama.” - Samael Aun Weor, Kundalini Yoga

The Yogi/Yogini who does not have a spouse can activate the flames of his Kundalini with Pranayama and Meditation. However, the complete, total, and absolute development of the seven degrees of power of the fire are only possible when practicing Sexual Magic with our priest/ priestess-spouse.” - Samael Aun Weor, Kundalini Yoga