The brain is a physical system. It functions as a computer. Its circuits are designed to generate behavior that is appropriate to your environmental circumstances.
Our neural circuits were designed by natural selection to solve problems that our ancestors faced during our species' evolutionary history.
Consciousness is just the tip of the iceberg; most of what goes on in your mind is hidden from you. As a result, your conscious experience can mislead you into thinking that our circuitry is simpler than it really is. Most problems that you experience as easy to solve are very difficult to solve -- they require very complicated neural circuitry
Different neural circuits are specialized for solving different adaptive problems.
Our modern skulls house a stone age mind