This is referred to as "Athmashtak" or "Nirvana Shataka" but is commonly
known as "Shivoham Shivoham...." composed by Jagadguru Adi Shankaracharya. Adi Shankaracharya reaffirms that the root cause of birth and death is ignorance. Once this ignorance has been dissolved and no longer existsone can reach the Sahasra-Chakra. One can look out towards the cosmos and some of the thoughts and feelings come to Shanakaracharya are expressed in the song where each stanza ends with "........ Chidananda Rupah Shivoham. Shivoham- The Shiva in All "

To teach the unity behind the appearance of multiplicity, to help realise the Adwaita (non-dual nature of existence), Adi Shankara, the great expounder of the Advaita school of thought. One day, Shankara was seated in meditation on the banks of the river Ganga.  Suddenly, he exclaimed, "Lord! I am yours; but, surely, you are not mine." His pupil, Thotakacharya was by his side then; he was astonished at this statement, which, according to him, went against the Advaitic principle. So, he asked him how he could ever declare any distinction between you and I. Shankara replied, "The waves belong to the ocean; but, the ocean does not belong to the wave. The wave is the ocean, but the ocean is not the wave." The main point of this argument is, the elimination of ego, the elimination of one's identification with the body and its needs, certifiable through the senses. For, one gets joy when these needs are fulfilled or grief when they are not fulfilled, anger when something comes in the way, pride when one wins
over that opposition.

To eliminate the ego, strengthen the belief that all objects belong to God, and that
all are holding them on trust. This would prevent pride; it is also the truth. Then,
when one loses something, one would not grieve. God gave it and later God took
away. Of course everyone hears almost all philosophers propose this course and
advise this reaction. But very few follow the advice themselves. This is the biggest problem; saying something but practicing quite the opposite, denying in practice what one asserts as precept.

NIRVANA SHATAKA (Atmashataka)

Mano buddhya-hankara chittani naham
Na cha shrotra jihve, na cha ghrana netre
Na cha vyoma bhumirna tejo na vayuhu
Chidananda rupah shivoham shivoham . (1)
(I am not the mind, intellect, thought, ego, or some form of the supreme being; I
neither have ears, nor tongue and I neither have nose (nostrils) nor eyes; I am not
the sky, earth, light or the wind; I am the fortunate, joyful, supreme being who is
the very emblem of truth, knowledge and eternal bliss. I myself am the spiritual joy of pure consciousness - Shiva; Shivoham, Shivoham.)

Na cha prana sangno na vai pancha vayuhu
Na va sapta dhatur na va pancha koshaha
Na vak pani padau na chopastha payoo
Chidananda rupah shivoham shivoham .(2).
(I am not the most essential air that everyone breathes. Nor a part of essential five gases related to bodily functions (which are Prana, Aparna, Vyana, Udana and Samana). I am not the seven-fold material (Rasa, Rakta, Mamsa, Medas, Asthi, Majja and Shukra) that help in body's physical development, I am not part of five coverings that help to build up the personality (food, air, mind, knowledge or wisdom and pleasure). Nor am I the five organs of action (which are speech/mouth, hands, feet, reproductive and rectum), I am the fortunate, joyful, supreme being who is the very emblem of truth, knowledge and eternal bliss. I myself am the spiritual joy of pure consciousness - Shiva; Shivoham, Shivoham.)

Na me dvesha ragau na me lobha mohau
Mado naiva me naiva matsarya bhavah
Na dharmo na chartho na kamo na mokshah
Chidananda rupah shivoham shivoham .(3).
(I have no likes or dislikes; Not I have any greed or delusion; I have no pride or
arrogant vanity; Nor am I jealous of anyone or in competition with anyone ; I do not need the four main necessities of life (which are Dharma (Law of Life), Artha
(Wealth), Kama (Desires) and Moksha (Liberation); I am the fortunate, joyful,
supreme being who is the very emblem of truth, knowledge and eternal bliss. I
myself am the spiritual joy of pure consciousness - Shiva; Shivoham, Shivoham.)

Na punyam na papam na saukhyam na dukham
Na mantro na tirtham na veda na yagnaha
Aham bhojanam naiva bhojyam na bhokta
Chidananda rupah shivoham shivoham .(4).
(I am not attached to any righteousness or sin; I have neither pleasure nor sorrow; I have no need for any Mantra; I have no need for pilgrimages ; I have no need for any sacred scriptures; nor do I perform any sacrifise or rituals; I am neither the meal nor the one who consumes or what is consumed; I am the fortunate, joyful, supreme being who is the very emblem of truth, knowledge and eternal bliss. I myself am the spiritual joy of pure consciousness - Shiva; Shivoham, Shivoham.)

Na me mrutyu shanka na me jati bhedah
Pita naiva me naiva mata na janma
Na bandhur na mitram gurur naiva shishyah
Chidananda rupah shivoham shivoham .(5).
(I have no fear of death, nor do I have caste distinctions; I neither have a father nor mother because I was never born; I have neither kin/relatives nor friends; I have no gurus and nor am I a disciple; I am the fortunate, joyful, supreme being who is the very emblem of truth, knowledge and eternal bliss. I myself am the spiritual joy of pure consciousness - Shiva; Shivoham, Shivoham.)

Aham nirvikalpo nirakara rupo
Vibhur vyapya sarvatra sarvendriyanam
Sada me samatvam na muktir na bandhah
Chidananda rupah shivoham shivoham .(6).
(I am free of thoughts and beyond imagination since I have no form; I am all pervading and exist everywhere; I am the king of all sense-organs; I am always
impartial to everything and everyone,; I am free from everything and I have no
attachment to anything; I am the fortunate, joyful, supreme being who is the very
emblem of truth, knowledge and eternal bliss. I myself am the spiritual joy of pure consciousness - Shiva; Shivoham, Shivoham.)