What makes Warren Buffett happy? The legendary investor is famous for his sunny, optimistic outlook and the pleasure he takes in life. And while he certainly enjoys studying investments and making money for himself and for Berkshire Hathaway's one million investors, the money itself doesn't seem to be doing him much good.

This week, Buffett sat down for a two-part interview with Judy Woodruff of PBS. In Part 1, he talked about the state of the economy and what Congress should do to fix American health care. In Part 2, he criticized Republicans' plans to lower taxes on the wealthy but also talked a lot about the things that make him happy.

That doesn't include his vast wealth, he told Woodruff. He may have Berkshire Hathaway shares worth about $77 billion, but "they have no utility to me," he said. "They can't do anything to make me happier. I'm already happy." All his money "can't buy anything for me that I want," he said. In fact, he added, he could be quite content with $100,000 a year.

So what does make Buffett, who seems to be one of the happiest people on the planet as well as one of the richest, enjoy his life so much? Here's what he told Woodruff. There's a lesson here for all of us.

1. Do work that you love.

Buffett has said in the past that he likes his work so much that he "tap dances" to the office every morning. When Woodruff asked for the secret to Buffett's enormous success and the fact that he's still going strong at 86, he answered, "The secret is to find what you love to do."

He added, "I tell the students to look for the job that you would take if you didn't need a job. I mean, it's that simple. And I was lucky enough to find it very early in life. I have more fun doing this than anything else I can think of in the world, and I have seen a lot of other things you could do in the world."

2. Spend time with people who inspire you.

"The second thing is to have people around you who make you feel good every day, and make you a better person than you otherwise would be," Buffett said. One of those was Susan Buffett, whom he married in 1952. Although the couple lived apart after she moved to San Francisco, which she preferred to Omaha and where she could pursue a singing career, they remained good friends and often vacationed and made public appearances together. Susan was a civil rights activist and a feminist, among other things. She died in 2004.

There's plenty of scientific evidence that the people you spend time with have tremendous influence over your mood and outlook, and even your health. And that the communities you create or choose to live in can have a profound influence on all those things, and even on your longevity. So choose wisely whom you spend most of your time with, both at work and at home. Buffett always has.

3. Get plenty of sleep.

Asked how much sleep he gets, Buffett responded, "I get quite a bit of sleep. I like to sleep." He usually gets about eight hours a night, he said. "I have no desire to get to work at 4 in the morning."

Here again, Buffett is on solid scientific ground. Getting enough sleep is vital to your health and mood--and may even help protect you from Alzheimer's. This is a very good habit of his to emulate.

4. Eat lots of junk food.

OK, seriously, don't follow Buffett's example when it comes to eating. During his interview with Woodruff, he was drinking a Cherry Coke, as he also does while at work. Every morning on the way to work, he picks up breakfast at a local McDonald's.

When Woodruff asked how he stays healthy, he answered, "Well, I think I stay healthy partly by being happy, actually." Not being stuck doing work he hates or working with people he dislikes has contributed a lot to his well-being, he said. "So I have gone very light on the diet advice."

In fact, he said, "I eat like a normal 6-year-old." True--but only if the 6-year-old didn't have parents nagging him to finish his vegetables. As always, Buffett has statistics to bolster his case. "If you look at the mortality statistics, I mean, 6-year-olds don't die very often. The diet's doing something for them."

5. Don't go chasing real estate.

Buffett still lives in the house that he bought in 1958. "I can buy anything, basically," he said. "I have been on 400-foot yachts. I have lived the life a little bit with people who have 10 homes and everything." That's fine for them, he says. "If I could spend $100 million on a house that would make me a lot happier, I would do it."

But he knows it wouldn't. "For me, that's the happiest house in the world. And it's because it's got memories, and people come back, and all that sort of thing."

Living in the same house for 59 years isn't for everyone, and I don't necessarily recommend it. (My husband and I bought a house about a year ago ourselves.) But there is a lot to be said for living well within your means. Living in a home you love but can only barely afford is one quick way to trash your finances, in case you don't have $77 billion in stock sitting in your safe deposit box as Buffett does. So it is smart to opt for affordable real estate, especially if you're beyond your 30s or 40s. Financial experts say paying down or eliminating your mortgage is one of the smartest things you can do by the time you're in your 50s or 60s.

6. Make the world better.

A fascinating experiment in which subjects were given money and told to spend it on themselves or to buy things for other people demonstrated that money can indeed buy happiness--but only if you use it for others. Buffett seems to know this. He signed the Giving Pledge with his billionaire friend Bill Gates 10 years ago, and has already begun the process of giving away 99 percent of his fortune. His billions don't have much utility to him, he said. "And they do have utility to others, so I have got this system to essentially try and translate that into vaccines and education and all of that sort of thing," he said.

You don't need billions to tap into that same source of happiness, and you can help make the world a better place at any donation level, say by picking a favorite charity or two and setting up a $5 or $10 monthly recurring donation. Try it--it will make you smile. It may even make you as happy as Warren Buffett.