I recently came across an old nursery rhyme that lists the six best doctors: sunlight, rest, exercise, diet, self-confidence and friends.

Why are they special?

Sunlight. A beautiful sunny day boosts everyone's spirits. Vitamin D from sunshine doesn't hurt, either. Sunlight is one of the reasons why I'm a snowbird from Minnesota who winters in Arizona.

Rest. As I get older, the power of rest becomes more important. But it is important at any age. We lead such busy lives. I've always been afraid that I might miss something. Forget it. Get your rest.

Exercise. All kinds of studies show that working out is good, but I don't need a study to tell me about exercise. I've been exercising all my life. It just makes me feel better, gives me energy to work more productively and, I hope, live longer. Back in the 1960s, I attended Stanford University for three months for its executive business program. Many fellow students were addicted to running, and they asked me to join them. I agreed, and it was one of the best decisions I've ever made. I've been a runner ever since and have run 10 marathons. Now I play a lot of golf. And I walk the courses whenever possible.

Diet. Eating a healthy diet is all about feeling great, having more energy, improving your health and boosting your mood. Good nutrition, physical activity and healthy body weight are essential parts of a person's overall health and well-being.

Self-confidence. This is extremely important in almost every aspect of our lives, yet many people don't believe in themselves as they should and they find it difficult to become successful. Confidence enables you to perform to the best of your abilities, without the fear of failure holding you back. It starts with believing in yourself. Confidence doesn't come naturally to most people. Even the most successful people have struggled with it in their careers. The good news is that you can develop confidence, just like any muscle or character trait, if you're willing to work hard.

Friends. I can't imagine what my life would have been like if I hadn't had such loyal and true friends. I am fortunate to number among my friends several classmates from first grade, as well as people I just met. My friends have saved my bacon over and over again. A few have actually saved my life. Friendship is like a bank account: You cannot continue to draw on it without making deposits. That's why I say the best vitamin for making friends is B1. We have wonderful opportunities to make friends wherever we go. I love meeting new people because I get a different view of the world.

A fascinating study from Harvard University tracked the physical and emotional health of 700 people. Researchers followed these people and tested them (e.g., blood samples, brain scans) for 75 years. The primary conclusion: Good relationships keep us happier and healthier.

That reminds me of a quote, commonly attributed to John Lennon although he might not have said it: "When I was 5 years old, my mother always told me that happiness was the key to life. When I went to school, they asked me what I wanted to be when I grew up. I wrote down 'happy.' They told me I didn't understand the assignment, and I told them they didn't understand life."

Mackay's Moral: Taking care of yourself is the best way to take care of others.

Harvey Mackay is a Minneapolis businessman. Contact him at 612-378-6202 or email harvey@mackay.com.