A familiar metaphor to describe zazen, and this life generally, is the moon in water.
It is a development of the mirror metaphor. Just like a mirror the water, when still, will reflect everything perfectly. So, as it were, there will be a second moon in the water. But, disturbed by the wind of ignorance, the water is disturbed, and waves form.
The ignorance is the belief that we are separate. But the critical part of the metaphor is deep faith that the wave – our sense of self, what we would call personal thought, feeling and experience – is not different from the ocean.
This faith, not making the ocean and the mind tranquil, is what is critical. Even if the reflected moon is a billion shards of light, because the wind is no longer ignorance, everything is still.