This essay is cross-posted from the Clearer Thinking blog. The question of how to achieve true happiness has been debated for thousands of years. In this article, we've summarized ten approaches to happiness, new and old, that are popular today.  How do you think about being truly happy? You might find that your personal views on this topic are captured by one of these ten popular theories. We hope that understanding these different theories will help you to better refine you...