The ego-sense creates the illusory “straw man” that seems real, but is actually just an artificial construct that acts as a nexus for our view of the world and our action in the world. Viewing our existence from the standpoint of the ego, we see ourselves as separately constituted beings, divided from all other beings and the world within which we live, and we strive to exist, grow, and aggrandise ourselves at the expense of other beings around us, and without concern for the environment within which we exist. This is, of course, ultimately a fictitious viewpoint, but it drives our understanding of ourselves and the world around us as long as the ego-sense is active. While rooted in the awareness of the Buddhi, the ego-sense also permeates the entire psychic Prana and the physical body, and thus infiltrates reactions even when the conscious mind has accepted the conceptual illusory nature of the separated, fragmented individual being.
Sri Aurobindo discusses the possible solutions: “to get rid of this idea, to dwell on the opposite idea of unity, of the one self, the one spirit, the one being of nature is therefore an effective remedy; but it is not by itself absolutely effective. For the ego, though it supports itself by this ego idea, aham-buddhi, finds its most powerful means for a certain obstinacy or passion of persistence int he normal action of the sense-mind, the Prana and the body. To cast out of us the ego idea is not entirely possible or not entirely effective until these instruments have undergone purification; for, their action being persistently egoistic and separative, the Buddhi is carried away by them, …, the knowledge in the intelligence is being constantly obscured or lost temporarily and has to be restored again, a very labour of Sisyphus. But if the lower instruments have been purified of egoistic desire, wish, will, egoistic passion, egoistic emotion and the Buddhi itself of egoistic idea and preference, then the knowledge of the spiritual truth of oneness can find a firm foundation. Till then, the ego takes all sorts of subtle forms and we imagine ourselves to be free from it, when we are really acting as its instruments and all we have attained is a certain intellectual poise which is not the true spiritual liberation. Moreover, to throw away the active sense of ego is not enough; that may merely bring an inactive state of the mentality, a certain passive inert quietude of separate being may take the place of the kinetic egoism, which is also not the true liberation. The ego sense must be replaced by a oneness with the transcendental Divine and with the universal being.”
Sri Aurobindo, The Synthesis of Yoga, Part Four: The Yoga of Self-Perfection, Chapter 8, The Liberation of the Spirit, pp. 649-650