The Gita spends a considerable amount of time describing and explaining the operation of the three Gunas of Nature. This is so because it is extremely useful for the seeker to understand how the “machinery” of Nature works and drives the choices and results of what the ego-personality tends to consider to be the action of “free will”. True free will does not operate until the soul is identified with the Supreme Person, the Purushottama.
Sri Aurobindo summarizes the role of each of the Gunas in the action of the individual: “Man in his natural being is a sattwic, rajasic and tamasic creature of Nature. According as one or other of her qualities predominates in him, he makes and follows this or that law of his life and action.”
“His tamasic, material, sensational mind subject to inertia and fear and ignorance either obeys partly the compulsion of its environment and partly the spasmodic impulses of its desires or finds a protection in the routine following of a dully customary intelligence.”
“The rajasic mind of desire struggles with the world in which it lives and tries to possess always new things, to command, battle, conquer, create, destroy, accumulate. Always it goes forward tossed between success and failure, joy and sorrow, exultation or despair. But in all, whatever law it may seem to admit, it follows really only the law of the lower self and ego, the restless, untired, self-devouring and all-devouring mind of the Asuric and Rakshasic nature.”
“The sattwic intelligence surmounts partly this state, sees that a better law than that of desire and ego must be followed and erects and imposes on itself a social, an ethical, a religious rule, a Dharma, a Shastra. This is as high as the ordinary mind of man can go, to erect an ideal or practical rule for the guidance of the mind and will and as faithfully as possible observe it in life and conduct.”
As the human individual evolves, eventually the highest sattwic level gets to the point where the individual attempts to act from a fully disinterested viewpoint for the greater good, and the being is prepared for the transition to the new divine standpoint, beyond the limits of the Gunas entirely.
Sri Aurobindo, Essays on the Gita, Second Series, Part II, Chapter 24, The Message of the Gita, pp. 572-573