Looking at the two verses from Chhandogya Upanishad, discuss the nature of self; the true sacrifice.

The nature of the self
This self of mine within the heart, is smaller than paddy or barley or mustard or millet or the kernel of a seed of millet. This self of mine within the heart is greater than the earth, greater than the intermediate space, greater than heaven, greater than these worlds.

The true sacrifice.
This one (the wind) that blows, this is surely a sacrifice … While moving, it sanctifies all this; therefore it is indeed a sacrifice.