You’ve known since childhood (some would argue since birth, or even before) that if you attempt to hold your breath consciously, you might pass out, but eventually, you will begin breathing again unconsciously, as long as you don’t split your head open on the floor.
In essence, you cannot completely stop the process of your breathing.
Put another way, breathing, or, your physical body’s natural drive to stay alive, much like the beating of your heart, is part of the ‘laws of nature’ or the ‘laws of the universe’.
You can manipulate these laws, you can exert a degree of conscious control over them; but you cannot override them or operate outside of them.
Now, if you really take a few moments to sit and become aware of this, you’ll see that it’s true not just for your breathing, but for a great many other things within our grasp, while we are here on Earth, in our physical bodies.