The document provides 15 rules for guiding one's life based on what is known about how the brain functions. Rule 5 discusses how the brain is not fully developed until our mid to late 20s, and brain development begins at conception. During adolescence, the frontal lobe is still developing so teenagers tend to be more emotional. Rule 12 discusses how emotions have a tremendous impact on our lives, both positive and negative. Negative emotions can become problems if they become too prominent.