When we exercise, our body releases chemicals called endorphins. Endorphins not only allow us to manage pain but also lifts our spirit making us feel happier.
The way we carry ourselves, our posture, our body language has a direct impact on our brains. When we are sad, we naturally will hang our heads. When we're angry or defensive, we'll naturally cross our arms. Therefore, if our bodies are reacting to our emotional state, then equally our emotional state will be impacted by our body language.
Standing with an erect posture will tell the brain that you are feeling confident. When we build abdominal strength, our posture improves because we have the strength to hold our torso up and as a result are sending messages to the brain that we are confident and happy.