Long after the size of the brain is established, it continues to undergo major stages of development. One of the last regions of the brain to mature is the prefrontal cortex – home of the so-called “executive” functions – planning, setting priorities, organizing thoughts, suppressing impulses and weighing the consequences of one’s actions. Did you catch that? The part of the brain that guides good judgment and decision-making develops last! In fact, the prefrontal cortex does not reach a level of genuine maturity until you are in your mid-twenties! As mature as you might look or feel, there’s still a lot of construction going on in your mind. When you feed your brain sex, drugs, alcohol or porn, you can seriously impede your mental development.