In zazen , as you practice letting go of your thoughts and internal dialogue, and bringing your mind back to the breath, the breath will slowly get easier and deeper, and the mind will naturally rest. The mind is like the surface of a pond. When the wind blows the surface is disturbed. There are waves and ripples and the image of the sun or the moon is broken up. When the wind quiets down, the surface of the pond becomes like glass.
Stilled mind is like a mirror.
It doesn't process, it just reflects. When there is a flower in front of it, it reflects a flower. When the flower is gone, the reflection is gone. The processing doesn't continue. When we hear a fire engine go by, we hear the fire engine.