The statements of the Upanishads were pronounced millions of years ago; but these statements are relevant even today. Yet there is a perennial doubt about knowing one's Self (Atma) or the Supreme Brahman because scriptures state that it has no qualities or attributes, and that it cannot be known by the sense organs; moreover, it is also stated that it is not an object to be known. So one may ask whether such a quest to know the Self is worth all the effort.
Lord Krishna allays these doubts in the Bhagavad Gita, asserting that this knowledge can be gained by approaching a Guru who is knowledgeable in the scriptures and is a knower of the Truth (Tatva Darshina). The Bhagavad Gita may be a political and administrative gospel where Krishna represents the country's culture and thought process in its climax, while it unfolds the ideal of excellence that every individual would aspire for, pointed out Swami Bhoomananda Tirtha in a lecture.
This excellence is made possible only with the individual's will power and strength. Purity of mind is important for excellence in performance.
Every individual is a psycho-physical complex being where the two aspects are seamlessly melded. Speaking, walking, or sleeping involve the coordination of the physical and the mental powers. But it is the subtle Self (Atma) pervading the entire individual's personality that is responsible for activating these physical and mental faculties.
The crucial message is that the mind is the crux of one's personality and it can be moulded. It is the inner instrument that can look and assimilate the external world on the one hand and also help us to look inwards to realise our inner Self. All the excellences based on thoughts and feelings pertain to the mind. It is capable of building the inner personality and giving the impetus for excellence.
God's power of Sankalpa is tremendous. While this manifested universe of matter and energy depends on God, He remains a supra-material presence and is the essence of consciousness, bliss and eternal existence. This same consciousness is also within us.