Kids have two of the essential ingredients for happiness mastered -- they know how to enjoy the simple things in life and they know how to say no. True, kids don't have to worry about paying the bills on time, but there's no law that says you can't worry about the bills and enjoy the blue sky at the same time.
According to Sonja Lyubomirsky, Ph.D., head of the Positive Psychology Laboratory at the University of California, people who can appreciate the small stuff are happier [source: Good Housekeeping]. Keeping a gratitude journal may help. At the end of every day, write down three to five good things about your day. Once you start noticing a pattern of things that make you happy (a crispy bagel in the morning, playing Frisbee with your dog), you'll be more aware of them and more likely to enjoy them as they're happening.
Kids have no problem saying "No" either. You might think of that as a negative, but in reality it's a huge asset. How many times have you taken on more that you can handle just because you couldn't say no? Saying yes all the time, to everybody, can leave you stressed and feeling run-down. So don't be afraid to say no. Don't think of it as being selfish but as honoring your existing obligations. Take a deep breath, say "Sorry, I have another commitment" and then smile. You'll be surprised to see that the world doesn't end just because you said no.