One recent study found that the cities where residents got the most restful night's sleep were also the places where people's happiness levels were highest. "The bedroom is where you relax and unwind," says Denis Cauvier, Ph.D., a business consultant and Lysaght's co-author. And when you consider that we spend a third of our lives in bed, investing in a new mattress, soft 600-thread-count sheets, or heavy-duty light-blocking window shades makes a lot of sense. In fact, you'll reap one of the most priceless things of all: a good night's sleep.

    Spend money on a gym membership instead of home equipment

    You might think you'd be a lot more likely to work out if you have a treadmill, stationary bike, or weight machine sitting right in your basement. Not necessarily. According to a recent survey by the Consumer Reports National Research Center, 37 percent of respondents admitted that they use their home equipment less frequently than they expected to.

    One possible reason: Working out with other people at the gym makes those sweatfests more enjoyable - and when people have fun exercising, they're more likely to stick with it, reveals an article published in the Journal of the American Academy of Physician Assistants. What's more, merging your workout with your social life will help you fit two important tasks into your overbooked calendar at once.

    "The gym basically automates your time with friends," explains Laura Rowley, author of "Money and Happiness: A Guide to Living the Good Life" and a financial columnist for Yahoo Finance. "You can see people you really want to see, which makes you happy and makes the expense feel worth it." If that's not enough of a reason to shell out that monthly fee, consider this: While you can slack off on the treadmill in your basement without anyone knowing, that militant spin instructor isn't going to go as easy on you. So in the long run, you'll be much happier with the results, too.

    Spend money on others instead of yourself

    If you want instant gratification, give some of your money away. In one experiment, researchers handed out $5 and $20 bills to students, asking half to spend it on themselves and half to dole the dollars out to other people. Those who gave the cash away reported feeling happier at the end of the day.

    "Not many things contribute to our happiness more than generosity," says Tal Ben-Shahar, Ph. D., a former Harvard lecturer and the author of "Happier." Consider donating $25 per month to your favorite cause （which you can deduct come tax time）. Don't have a cause close to your heart? Check out charitynavigator.org, which catalogs organizations by topic （animals, environment, health, etc.） and even rates charities, so you can be certain your contribution really will make a difference.

    Or do something good close to home: Researchers at the University of Pennsylvania's Wharton School have found that we're more motivated to help others when we have some personal connection to them. Find local charities that strike a chord - food pantries, the humane society, a homeless shelter, or a local museum or library - and write a check to help them out. On a smaller scale, treating a friend to lunch for her birthday or buying your boyfriend his favorite flavor of ice cream can make you feel warm and fuzzy, too.joozone.com