'Next follows the explanation of the Infinite as the Self: Self is below, above, behind, before, right and left—Self is all this. 'He who sees, perceives, and understands this, loves the Self, delights in the Self, revels in the Self, rejoices in the Self—he becomes a Svarâg, (an autocrat or self-ruler); he is lord and master in all the worlds. 'But those who think differently from this, live in perishable worlds, and have other beings for their rulers.

In plain words: The teacher says it again using 'the Self', meaning your deepest true being: the Self is on every side and is all this. A person who truly understands this loves and delights in the Self. That person rules himself and is free everywhere. Those who think otherwise stay under the control of others and live in a world that passes away.