Just from what I learned in a Stress and Anxiety course smiling can reduce stress which would help to influence your emotional state. This chapter discusses how smiling can boost your emotional state by the movement of muscles in your face. This involves you smiling which increase activity , and influence expressions which influence your emotions. The book uses the example if you watch a scary movie that would result in your being horrified and then see a scary face that would increase your emotional state and increase your reaction. A smiling face can increase your mood and be more likely to make positive decisions.