01/04/2008 01:26 pm ET Updated May 25, 2011

What to do for YOUR happiness project: Go outside.

I'm working on my Happiness Project, and you should have one, too! Everyone's project will look different, but it's the rare person who can't benefit. Join in -- no need to catch up, just jump in now.

This happiness assignment is easy. Go outside.

Go outside into the sunlight; light deprivation is one reason that people feel tired. Research suggests that light stimulates brain chemicals that improve mood and increase motivation.

For an extra boost, get your sunlight first thing in the morning.

Now, I'm the kind of person who loves to sit around the house in my pajamas. If I can manage it, I enjoy the occasional day when I never step foot out of my apartment.

But even though I love staying in, there's nevertheless something slightly oppressive about being inside all day.

And going from your front door, to the car door, to the office door, and then in reverse, isn't much better.

At least for me, unscientifically speaking, spending time outside gives a feeling of freedom, of connecting with the seasons (even when the weather isn't ideal), of breathing fresh air, of not being so trapped by a schedule that I can't be out in the world.

Plus, if you use your time outside to go for a walk, you'll get a double benefit for mood and energy. Because I live in New York City, I get a lot of opportunities to walk around outside, and I know it boosts my spirits.

If possible, push the directive to "Go outside" a little further, and try to build some more outdoor time into your life. Go hiking, go birdwatching, get a dog, shoot hoops in the driveway.

People in industrialized countries spent about 93% of their time inside; don't forget how energizing and cheering it can be to go outdoors.

If you need some help summoning up the energy to venture out, check out this post for ways to boost your energy.