The Bhagavad-Gita ["Song of God"] is among India's most beautiful and profound texts. It is a truly spiritual work, and touches upon the nature of the smaller self (ego) and higher (Soul) and highest (Spirit) Self. In that text, Krishna transforms himself into other creatures-- some say, into every other creature. While he is "talking to Arjuna," he is also Arjuna! He is both teacher and perennial learner, both horse and rider, cat and mouse, pursued and pursuer. Thus does he bring into being this beautiful world, as a dream of the divine Mind.
This does not mean that the world is "unreal," but that its reality is relative, not absolute. Only Mind has absolute existence, and that is why enlightened mystics often call It the "Absolute." For everything else in the cosmos exists only relative to the existence of this Mind.
Without It, the entire cosmos would "blink off," disappear. Yet even if the entire cosmos did disappear, it would have no effect whatsoever on the real (absolute) existence of the one Mind. (This is the "One," God, divine Mind, cosmic Mind, or Love.)
I am delighted to hear that you are reading such a profound and wonderful text as the "Song of God." It is a breath-taking and awe-inspired reminder that this passing world is only a dream, a "virtual reality," existing in Mind only. And, as Krishna says, even reading this text generates good karma!:)
That is, everything is Mind, as are we. This gives birth to that most famous realization in Hindu mysticism, Tat tvam asi, which means, "That thou art." You begin to identify with every thing in your experienced cosmos, since it is all a dream within a mind. There is no "out there."
In the vastness and immensity of this realization, the ego-- the name on your driver's license and birth-certificate-- is seen as a minor and not very important "game," a "role" being "played on the stage of earthlife" by your Soul. Thus, in growing into enlightenment (filled with Love, and nothing else), the ego dissolves into a much brighter and higher Loveself. This is how the enlightened person "denies" and even "denounces" the ego. This re-identification of the self as a higher (Soul), or even the highest (Spirit), Self results in bliss (ecstasy), for this is the "reward" of the cosmic Mind (God or Love).
This is the most complex subject in the entire cosmos. If you have any further questions, please do not hesitate to drop me a line or two.:)