Your brain weighs about three pounds, but it controls everything you feel. When something worries you, your brain sends a signal to your body. Your heart beats faster. Your muscles tighten. Your breathing gets quick. This is called the stress response. It was designed to help our ancestors survive danger, like running from a wild animal. The problem is that modern stress, like a big test or a fight with a friend, triggers the same response. Every year on October 10, World Mental Health Day reminds us to take care of our minds. Scientists have discovered that certain activities can calm the stress response. Exercise tells your brain to release chemicals called endorphins, which make you feel better. Deep breathing slows your heart rate and tells your brain the danger has passed. Talking about your feelings with a trusted adult helps your brain process difficult emotions. Sleep is also essential. When you sleep, your brain sorts through the events of the day. Without enough sleep, your stress response becomes more sensitive. Most kids need nine to eleven hours of sleep each night.