The Gita consistently holds that the true source and reality of our existence is the supreme divine spirit, the Purushottama and that all of manifested Nature is the action of the Purushottama. The ego and the outer Nature are not our true selves but an outer shell. The true Self, a “portion of the Purushottama” is the Jiva. Sri Aurobindo describes the Jiva: “He represents in Nature the power of the supreme Spirit, he is in his personality that Power; he brings out in an individual existence the potentialities of the Soul of the universe. This Jiva itself is spirit and not the natural ego; the spirit and not the form of ego is our reality and inner soul principle.”
This brings us to the meaning of Swabhava: “The spiritual Nature which has become this multiple personality in the universe, …, is the basic stuff of our existence: all the rest is lower derivation and outer formation from a highest hidden activity of the spirit. And in Nature each of us has a principle and will of our own becoming; each soul is a force of self-consciousness that formulates an idea of the Divine in it and guides by that its action and evolution, its progressive self-finding, its constant varying self-expression, its apparently uncertain but secretly inevitable growth to fullness. That is our Swabhava, our own real nature; that is our truth of being which is finding now only a constant partial expression in our various becoming in the world. The law of action determined by this Swabhava is our right law of self-shaping, function, working, our Swadharma.”
Sri Aurobindo, Essays on the Gita, Second Series, Part II, Chapter 20, Swabhava and Swadharma, pg. 502
Sri Aurobindo Studies 