Upanishad means to sit close. You can sit close to someone on the physical plane but there may remain a huge distance in the mind. The Upanishads talk about mental proximity.
In the Isha Upanishad, Isha represents the I or energy and sha is the completeness: the full, silent, vast, divine. The invocation begins with an exclamation of fullness, or That is full . What is that fullness which is being invoked It is the state of meditation, a state of being that is neither the state of dreaming, sleeping nor waking. After the experience, the master tells the student: That is fullness. The invocation ends thus: Om Shanti, Shanti, Shanti . No happiness or knowledge can happen without peace. The first step to peace is to realise that everything is complete.
The world that we see, of the senses, is but a small part of totality. Completion is like the zero, full and complete. Completeness settles the mind so you can reflect and this turning of the mind inward is spirituality
Isha the divine permeates the whole universe and is addressed as energy, not as a person. Everything is permeated in that one consciousness. Wake up and see that the whole universe is infinite and that your inner space is as complete as this universe. See that the universe is permeating your spirit; nothing is dead. Honour your body and enjoy this world by renouncing it. Just step back. Clinging to it brings you misery . Renunciation is protection for your soul. Pleasant and unpleasant events, though they may appear different, are both made of the same divinity. Unpleasant events make you stronger, while pleasant events expand you. Renunciation is being in the present moment totally. Realise that the universe is permeated with love and abundance and that your needs will always be taken care of.
Cultivate the strength to renounce in misery and be willing to do service when happy. Aspire to live for 100 years doing your work. Life here is to get over your karmas, which you can do only in this body; and the knowledge you get, impart to others. Do your action 100 per cent, but dont be feverish about it. Whatever you have not given or loved, you will come back to do it. Keep doing your work and keep renouncing. We cannot really know the entire universe and its magnanimity because of our limited ability to perceive . The brain works on a frequency channel ; our sense organs have limited capacity but the universe, like the divine, is limitless . In this limited time we call life we keep on doing our work.
Those who do not realise or attend to the self in life live in darkness and when they leave the world they will be in darkness also. When you leave the body in meditation, you achieve a higher plane.
How do you know if you have realised the Self The atma is motionless; it is the substratum of the universe and everything is in it. It is space that is faster than the speed of light, faster than the mind; you can never comprehend the Self through the senses. The seer, the one who sees, who feels, understands, is the Self. This cannot be comprehended through the senses, yet every action in the universe is run through consciousness . A seed sprouts because there is consciousness in the seed. The entire universe is filled with this prana or life and you are the container of this, not the content.