What is said to be the source of our sorrow lies on our wrong perception about the world and myself. Since limitless is our nature, we can't accept comfortably being limited by the world, including my body-mind-sense-complex. This is all because of not knowing my true nature being absolute existence - sat, by which everything can come into being as object of awareness. By this ignorance, we are taking the limited nature of asat onto myself and taking asat to be limitless in the sense of capability of giving fulfilment.
How can my life become better if I know my true nature? What is the use if I know I am absolute existence, but I only experience existence in this body? What is the use if I know that I am limitless but I always feel limited? What is the benefit of knowing I am the consciousness which make everything here having its being to be aware of? It is worth to analyse further.
What is the world? The world is object of my perception. The looks of the world outside is how it is perceived in my mind. Therefore frankly speaking there is no outside world at all. What is in my mind is the world I know. The world that other people know will not affect me, only the world I know can bring me sorrow or happiness.
We know that object and subject are having the dependency to be existing from previous class. When I opt out myself to be the seer, there will be no object exist to be seen. In the same time, when there is no object to be seen, I am not a seer. When seer and seen are negated, what exist is only me - consciousness who is aware of the world comes and goes (changes), and aware of the seer who identify with this body-mind-sense-complex comes and goes. While subject and object (consist of the world) is depended on me - the consciousness to be there, how can they affect me? No matter how the pot looks like, it will not affect the clay as long as the clay is not identifying with the pot. In the same manner if Arjuna understands that he is the basis for the all beings to exist, without identification with them, how can there be someone to be killed and himself to be the killer?
Being the very basis for the entire world to exist, means it is pervading the entire world, thus indestructible. 1) Because being the reality of the entire world, there is no second reality which can destroy ātmā. How about asat destroys sat? 2) When two things are having different realm of reality, they can't destroy each other. The dream tiger can eat me up in the dream, but couldn't eat up the wakened me. Or can ātmā destroys itself just like any living being which perishes by its own in one day? 3) Ātmā is not born and not subjected to change, therefore there is no self destruction on the part of ātmā. Perhaps it might be argued that one part of subject can destroy the other part. 4) That is also not possible because ātmā is the undivided homogenised substance, where parts are not there. Therefore no one can bring about destruction to ātmā (2.17).
If I am not the one who do the action, who does? Everything in the realm of creation is the modification of māyā. Even though sat-cit-ānanda-brahman is the reality of the creation, but without māyā-sakti, creation will not be there. Therefore brahman is unmanifest and māyā/prakrti is manifest name and form. The body-mind-senses are prakrti, and the entire world is also prakrti. All are modifications - guna of prakrti alone. And these two prakrti (subject and object) are engaged with each other. Any perception or action is only a contact between one prakrti which is in the form of instruments (subject) with another prakrti which is in the form of objects. Subject engages activities with object. Only the one who identifies with the subject is the doer of the activity. On the other hand, when identification is not there, one is not the doer. Activity is to be done, but do not identify as the doer of the actives. When there is no doer-ship, there is also no experiencer-ship, then one is free no matter what is unfolded in this experiential world (3.28).
Action is to be done, but I am not doing the action. This is not easy to assimilate. Therefore one should have the attitude of karma-yoga in one's action, by doing one's own duty set aside one's likes and dislike, and accepting the result of action with the evenness of the mind, for purification of mind (2.48). Then one is qualified to own up the limitless nature of oneself by ātmā-jñānam.