AVG 2.12

Chapter 2 (The Seekers Joy at Self-Cognizance): Verse 12
अहो अहं नमो मह्यं एकोऽहं देहवानपि ।
क्वचिन्न गन्ता नागन्ता व्याप्य विश्वमवस्थितः ॥ २-१२॥

PURPORT:
I remain amazed; salutations to myself!
Though I am actualized in this body, I am One.
I neither go anywhere nor come from anywhere,
but, I am present, pervading the universe.

TRANSLITERATION:
अहो अहम् नमः मह्यम् एक अहम् देहवान् अपि ।
aho aham namaḥ mahyam eka aham dehavān api ।
क्वचित् न गन्ता न आगन्ता व्याप्य विश्वम् अवस्थितः ॥ २-१२॥
kvacit na gantā na āgantā vyāpya viśvam avasthitaḥ ॥ 2-12॥

MEANING:
aho (अहो)  = astonished! [as an exclamation of being pleasantly surprised at himself]
aham (अहम्) = I am
namaḥ (नमः) = salutation/adoration
mahyam (मह्यम्) = to myself/for me
eka (एक) = one (as in one without duality of any kind)
aham (अहम्) = I
dehavān (देहवान्) = having a body/being embodied
api (अपि) = even (as in ‘even though I am embodied’) ।
kvacit (क्वचित्) = anywhere/in whatever place
na (न) = not
gantā (गन्ता) = going (as in ‘going from anywhere)
na (न) = not
āgantā (आगन्ता) =  coming
vyāpya (व्याप्य) = permeable/pervading everywhere
viśvam (विश्वम्) = universe
avasthitaḥ (अवस्थितः) = to be present/to have its place or abode/existing ॥ 2-12॥

COMMENT:
Janaka here talks about his realization of the underlying oneness that connects his physical body to the universe. His joy at realizing that the material constituents of his body is in reality in a harmonious continuum with the rest of the matter within the universe is palpable (repeated use of the phrase "I remain amazed; salutations to myself!" across this verse as well as subsequent ones attest to this).
Our bodies are chemical machines with no notion of separateness from the nature that surrounds us. After physical death, the remnants remain with the flow of sentient and non-sentient matter within the universe - our bodies come from this and to this it returns. The fortuitous collection of atoms that temporally came together to form our bodies does not desire in any sort of a manner towards an afterlife or immortality or a state of eternality. All the body does during its brief sojourn here is two things: making sure that internal equilibria are maintained via homeostasis and making sure that the genetic imprint of the body is passed on via the reproductive activity.
In this regard, the brain is a part of the inter-dependent mechanism within the body that strives to manage, maintain and regulate these two processes. So, one might ask, if this were the case, where do feelings of impermanence, unhappiness and the resultant suffering come from? How is thought (and thinking) connected with all of this if the body is a chemical machine that strives to homeostasis and reproduction?
This is where the influence of shared culture and the conditioning of thoughts with the artifacts of culture come into the picture. Culture imposes its own conditioning upon the brain in the form of preferences, choices and perceived pleasurable outcomes. In a deeper fundamental manner, the body does not care too much for happiness or pleasure as long as its basic functions of homeostasis and reproduction are satisfied. Even if the body does not care too much, our thoughts are conditioned towards craving and permanence within the realm of pleasurable outcomes - outcomes that are deemed pleasurable based on our cultural prejudices and leanings. The innate insistence to keep desiring more and more of the same is really the projection of our feelings of permanence upon those aspects of our life. Such projections of permanence are further driven by the sensory inputs that amplify our latent prejudicial projections.
Of course, as far as the body is concerned, notions of permanence are really anathema - as the body is focused on homeostasis and reproduction - not on permanence of any manner. So, we have this interplay between two forces - where the body wants to carry on its basic functions that evolution and programmed genetics have set out to perform while the force of conditioned thoughts within our brains puts our thoughts/brains at odds with the body - leading to feelings of body/mind separation and the resultant dualities. The fear and confusion borne out of this dynamic interplay is the measure of misery we bring to bear upon ourselves as well as our fellow sentients in this world. Our overarching insistence towards the search for permanence in the objects we cherish as well as the sense of separation that such a search imputes within ourselves results in suffering and dissatisfaction. While the body as a unitary whole will arise, endure and dissipate, it is the process of thought and thinking that leads us to a place of dissatisfaction, unhappiness and suffering.

An additional note: The sense of wanting to attribute a notion of permanence to entities per our cultural conditioning is the process of thinking and thinking is the process by which we impute an imaginary sense of permanence to entities deemed so per our cultural conditioning processes.