The Mystry of our Inner Voices in Our Minds

One of the mysteries that we are not conzigent about it and we take it for granted is why our brains is thinking all the time? This goes also for the rest of the animal kingdom? This is a mystery of our creation. Imagine if our brains are not thinking? Is this has to do with our survival in our environment? Then what is the mystery of our the instinct desire for our survival? It looks that one mystery collides with another mystery and we are always in square one.