Extroverts, those outgoing, gregarious types who wear their personalities on their sleeve, are generally happier, studies show. Some research also has found that introverts, who are more withdrawn in nature, will feel a greater sense of happiness if they act extroverted.

Experts aren't entirely sure why behaving like an extrovert makes people feel better. One theory is that being talkative and engaging influences how people respond to you, especially if that response is positive. Others speculate that people get more satisfaction when they express their core self and opinions. Another possibility: Happiness might come simply from having successfully completed a goal, such as giving a speech.

"If you're introverted and act extroverted, you will be happier. It doesn't matter who you are, it's all about what you do," said William Fleeson, a psychology professor at Wake Forest University in Winston-Salem, N.C.

Other studies have shown that extroverts are more motivated than introverts. Researchers believe this is due in part to extroverts' greater sensitivity to dopamine, a neurotransmitter that plays a big role in behavior driven by rewards.

Clark Powell considers himself an introvert, but his job as vice president of a media relations and multimedia production firm means he often must act out of character. "My job requires me to be on TV…and to do media training and presentations in front of large groups of people, as painful as that can be sometimes," said the 46-year-old in Columbia, Ohio. Though he may dread making a presentation, he says he is exhilarated afterward. "I do feel a sense of relief and elation, but I don't know if that's because of the experience or because the experience is over," he said.