The ascetic paths of Yoga try to achieve liberation and realisation by denying the action of the life-energy and suppressing or abandoning it. The integral Yoga, in embracing action in the world, necessarily has to address the action of the prana in carrying out its developmental process. A weak and easily tired or distracted force cannot achieve the integral realisation. Thus, the pranic force must be marshalled, concentrated, directed, and put to work in the being. Traditional paths of Yoga used various physical and psycho-physical methods, such as Pranayama to gain mastery over and control of the Prana. Sri Aurobindo notes that while this control is necessary, it must be capable of being exercised independent from any specific physical routine or practice.
“The same mastery must be got by the seeker of the integral Yoga; but he may arrive at it by other means and in any case he must not be dependent on any physical or breathing exercise for its possession and maintenance, for that will at once bring in a limitation and subjection to the Prakriti. Her instrumentation has to be used flexibly by the Purusha, but not to be a fixed control on the Purusha.”
The importance of the free and powerful play of the pranic Shakti is emphasized by Sri Aurobindo: “If it is full of strength and swiftness and a plenitude of all its powers, then the mind can go on the courses of its action with a plenary and unhampered movement. But if it is lame or soon tired or sluggish or weak, then an incapacity is laid on the effectuation of the will and activity of the mind. The same rule holds good of the supermind when it first comes into action. There are indeed states and activities in which the mind takes up the pranic Shakti into itself and this dependence is not felt at all; but even then the force is there, though involved in the pure mental energy. The supermind, when it gets into full strength, can do pretty well what it likes with the pranic Shakti, and we find that in the end this life power is transformed into the type of a supramentalised Prana which is simply one motor power of that greater consciousness. But this belongs to a later stage of the Siddhi of the Yoga.”
Sri Aurobindo, The Synthesis of Yoga, Part Four: The Yoga of Self-Perfection, Chapter 14, The Power of the Instruments, pp. 705-706