We don’t control our autonomic nervous system. The functions that keep us alive operate from an older part of the brain that is not accessible to our conscious mind. The closest we come is our breathing. We can consciously breath, but we do not have to think about breathing and we cannot stop our breathing. Perhaps this is attributable to how our brains developed over the millennia. Or perhaps it is a deliberate feature of human life that we should not have this control. We could use it to defeat what we are here for (a different topic).
Viewed another way, our autonomic systems represent the natural realm, while the conscious mind represents the human realm. The natural realm is the firmament that is always changing, always flowing. It will not be governed by the human realm. Human affairs exist in the juncture between the firmament that is inaccessible and those things that can be affected by human action.