Writer Jean Stafford scoffed, "Happy  people don't need to have fun," but studies show that the absence of feeling bad isn't enough to make you feel good;you must try hard to find sources of feeling good. Research shows that regularly having fun is a key factor in having a happy life;people who have fun are 20 times more likely to feel happy. Recently, I noticed a pattern among activities that people find fun: _ . There's something about having a playful purpose,of trying to achieve something that makes an activity more fun. For example a friend told that she loved visiting flea markets and antique stores to look for old globes-not fancy ones,but cheap ones. She has a rule that she'll never pay more than$20. She's the kind of person who loves wandering around in those kinds of shops in any case,but having a mission makes it more fun, less aimless. For that matter,having a collection of any sort is a very popular way to have a mission. You get satisfaction whenever you find another piece of blue sea glass on the beach or another out-of-print book by Charlotte Yonge in an old bookstore. Taking photos is a common way to incorporate  a mission into traveling. Not only does this help keep memories vivid, it also makes you more attuned to your environment while traveling. For example,during my most recent visit to New Haven,I had a lot more fun wandering around once I set myself the mission of taking tourist photos of my own romance. Why is this true? The First Splendid Truth holds that to be happier,you have to think about feeling good and feeling right,in an atmosphere of growth. The more I've thought about happiness,the more surprised I've been at the importance of the "atmosphere of growth." I think this is a huge engine of happiness, and when you have a mission, you create an atmosphere of growth whenever you pursue that mission. Have you found a way to have a mission? What is it and does it boost your happiness? The author explains the key factor in having a happy life by  _  .
making a comparison presenting numbers stating common sense using examples