According to an article in Time magazine feeling happy is influenced by what the brain does and also what the face does. The research shows that people can change their mood by adapting facial expressions.
Recent studies have provided support for the universality of basic emotions such as joy or love for example, by showing that both blind and sighted people display the same facial expression for genuine happiness and display the same fake or social smile when feigning real happiness.
The article outlines various studies which show that adjusting facial expressions can change how you feel. To read the article click here