You can help yourself get out of a bad mood by spending time imagining happy things according to a recent study. Although this is clearly a small study it adds to others on gratitude and guided imagery. Of course we know there is a Christian source too–scripture. By the way, this method will NOT cure an episode of depression, which affects much more than moods. As a habit however, it may aid in prevention.
Philippians 4:8 —Finally, brothers, whatever is true, whatever is honorable, whatever is just, whatever is pure, whatever is lovely, whatever is gracious, if there is any excellence and if there is anything worthy of praise, think about these things.