Sri Aurobindo translates Mundaka Upanishad, Chapter 3, Section 2, Verse 2: “He who cherishes desires and his mind dwells with his longings, is by his desires born again wherever they lead him, but the man who has won all his desire (Or, ‘finished with desires’) and has found his soul, for him even here in this world vanish away all desires.”
The key to realisation is the shift of the psychological standpoint from that of an individual, limited and separated from the rest of the world, who tries to gain personal fulfillment of desires, to that of the divine, which recognises the oneness of the entire creation and the inter-dependence of all the beings and forms with one another, and which seeks to express and carry out the will of the divine in its manifestation of the universe. That shift implies the release of desires. It is a recurrent theme in various Upanishads that the vital force of desire drives the focus, attention and action of the individual and that the direction of the life, and indeed subsequent lives, is set by this focus.
Desire stirs up the “mind-stuff” and thus, prevents it from having the state of serene and glad receptivity that the Rishi has already described as the condition for realisation. The issue here is not the artificial suppression of desires on some external moral grounds, but the removal of the force of desire entirely so that neither by its pressure of action, nor by the pressure of its suppression, can it disturb the mind-stuff. “Serene gladness of mind” is the characteristic that illustrates the quieting of the desire-mind.
Giving up the motive force of desire-fulfillment does not necessarily imply inaction or inability to act in the world. Desire is the individual deformation of the will of the divine in the expression of the universe. Once the standpoint has been shifted, the individual can act in the world without the hungry seeking, the frustration of denied desire, or any expectation of result, keeping a quiet mind and heart turned to the Supreme.
Sri Aurobindo, The Upanishads, Mundaka Upanishad, pp. 193-210