Here is a short summary of an interesting study that shows how moving facial muscles in a particular way can lead to a shift in your mood.
Research studies have demonstrated that asking people to change their facial expressions leads to a shift in their moods. Participants were given specific instructions on which facial muscles to move and how. In this example, the instructions that were provided were characteristic of the movements of an angry expression, but importantly, they were NOT told to mimic any particular emotion. When asked how they were feeling, those participants were more likely to describe themselves as feeling angry than those given instructions characteristic of a different emotion. They also showed more physical signs of anger in regard to heart rate, skin moisture, and finger temperature. Retrieved from: “Doing CBT” by David F. Tolin