Chapter II, Verse 45
The objects and forms, which are the manifest, obvious, and perceptible existence that is seen, perceived, and known, form the mind of a human being. Thus, the mind sense records the knowledge of objects, whose constitution is based on the three gunas sattwa, rajas, and tamas (in Hindi). Therefore, the knowledge of objects, subjects, and their relationship will always keep the mind in the field of gross objectivity.
So the mind sense will always be in the field of objective difference, or duality, where the sense of otherness will always exist in the mind consciousness of a human being, never allowing a person with mind to realize the fundamental, essential Truth, forever eternal, unchanging, unchangeable, unmanifest, and unproduced the ultimate Unity Source-Substance, which manifests all the forms and all the visible or invisible existing material substances in the world.
Therefore, Lord Krishn, the Knower of the fundamental Truth of this essence in Oneness, is giving the secret knowledge and technique: how to become able to realize Unity, or Immortal Existence, which is all-permeating, provided the human being transforms his always dualistic mind sense and then realizes the immortality and indivisibility of this Shyamtaa or Krishntaa (in Hindi) essence that permeates the entire nature of prakriti (in Hindi). For that, Lord Krishn's personal advice to Arjun and to mankind as a whole is that the human mind should transcend the knowledge gained through the experience of the objects belonging to the three gunas (in Hindi).
This realization of the ultimate existence of Oneness, which is the Self, will establish the mind of a human being in the state of Oneness, Shyamness, Krishnaness, or formless, Absolute Clear Blueness, without which not even the vision of a human being the sight that watches white light can come into manifestation. This Shyamness, Krishnaness, and ultimate, formless Blueness Pure Existence is eternal.
From this fundamental Knowledge, sattwa (in Hindi) becomes the light of consciousness. So the human being will be established in the state of nirdwand and nitya sattwasth (in Hindi). And since in this Oneness, Shyamness, Krishnaness, and Absolute Clear Blueness there is no sense that "I need to possess," or, "Having possessed, I have to protect, or save, or keep," therefore, being established in this realization of the essential, true Self, a human being will gain the state of niryogchhaym (in Hindi), because he is now established in the state of pure Self, or Aatma (in Hindi), and has become free from the mind sense of duality. Thus he has gained the state of Aatmvaan (in Hindi), and is no longer a doubtful, human mind sense. His intellect or mind has gained stability in its source, the ultimate Pure Shyam Blue Space, Unity, or Oneness, which permeates the visible and invisible forms.