Upanishads are the conversations between a Guru and a Seeker. Adhyatma Upanishad is part of that. I just tried to put the essence of Adhyatma Upanishad and hope it will help you to quench your thirst of spiritual quest.

Here it goes –

This body is made of five elements: earth, water, fire, air and ether. An eternal which is soul lives inside the cavity of the heart. It lives inside the earth, but the earth doesn’t know it; it lives in all the elements but no elements are aware of it.

The mind is also the body of the soul, but the mind isn’t aware of it; likewise the intellect and the ego are the body of the soul, but they are not aware of it.

Moreover the birth and death are also the body of it, but they are not aware of it.

[Here, I would like to correlate one thing: as the soul leaves the physical body and it is named as death (but it remains with mental body). Later on when soul goes higher and higher in upper dimensions, it has to leave the mental body also. Whatever is with soul is not soul.]

[The word "Brahman" which is very frequent in every Upanishad connotes the eternal soul. It is never meant to any caste or religion.]

The things which are with soul are just objects, the “Brahman” is real else is manifestations. And all the illusions are broken when the Brahman starts taking its place.

With the practice of feeling “I am that”, the Brahman; one starts getting to know what is real and what is unreal. The wider the gap of understanding between the real (soul) and unreal (objects), the more Brahman will evolve. And, in that case the; attention shifts from the five senses to the self.

As an empty pot has the same air inside and outside of it, likewise the self is same everywhere inside or outside the body.

Divinity exists everywhere and to feel and see that way causes truth to explore and untruth to fade away.

When inner merges with outer, and oneness comes – this stage is Samadhi, the highest stage of unity. With Nirvikalp (choiceless) Samadhi, one gets self-realization – and it ends the ignorance.

The eternal soul that is self, it is everything – it is the God, it is the Goddess, it pervades everywhere. And apart from it, nothing exists.

The self is free from duality, so it can’t be observed and it cannot be observer also – it is one and will remain one.

To listen “That Are Thou” (Tat Twamsi) is the right listening.

All the conditioning of the mind, no matter how big or how many they are, erased in Samadhi and the most natural qualities of a person take place.

A person after getting self-realization feels that he has nothing to renounce now, he finds himself blissful; un-compared, unique and natural. He feels that he is God like, infinite, imperishable, pure and silent.