One of the best decisions I've ever made in both my business and personal lives was to start running. I remember this like it was yesterday.

I was attending an executive program at Stanford University's graduate school of business back in the 1960s. Several foreign businesspeople who were also attending went out for a run every day. They asked me if I would like to join them, and I thought it sounded like fun. From that simple invitation grew a habit that has lasted a lifetime.

Running not only has kept me in good shape, but it has sharpened my focus. The benefits of physical activity on both the body and mind are well-documented. My personal experience tells me that when I don't run -- or walk briskly, as I have been more likely to do in recent years -- I lose some momentum. Running clears the cobwebs and renews energy.

Two hip replacement surgeries sidelined me for the past few years. But I just can't give it up. With my doctor's blessing, I entered and completed the Rock 'n' Roll Half-Marathon in Phoenix on Jan. 20. I didn't set any records, but that's not what matters. I finished, just as I did in 10 previous full marathons, including the 100th running of the Boston Marathon.

I saw a remarkable range of participants in the half-marathon. One guy carried the American flag for all 13 miles. I saw a blind woman tethered to a guide runner, who served as her eyes, describing the scenery and painting the picture. People pushed baby strollers for the distance. Runners dedicated their races to the memory of loved ones and causes. The motivations are endless.

Anyone who finishes a marathon -- or a half-marathon -- has won. The proof is that in earlier days, people would ask you what your time was. Now the question is, "Did you finish?"

For most runners, the key to running a marathon is to understand that it is not so much a physical as a mental challenge. Your body does not want you to run a marathon. Your mind must make you do it. Therefore, you have to develop a rationale so powerful, a determination so strong that it will enable your mind to overcome the vigorous protests of your body.

Marathon legend Grete Waitz, winner of nine New York Marathons and two London Marathons, plus five world cross-country championships, lived by the motto, "If you give up, you lose."

The race Waitz is best remembered for was the New York Marathon in 1992. Her time: 5:32:35. That's right, more than five hours. She ran hand-in-hand with the event founder, Fred Lebow, who was fighting brain cancer. Grete's quote after the race went something like: "The true heroes are not us up in the front but those who are there at the back of the pack because they are there for four to five hours."

In 1987, I ran my first of five New York marathons. Approximately 23,000 runners started the race, but only 20,000 finished. The last finisher was Bob Wieland, a Vietnam veteran, who ran it in four days and two hours. He had no legs and ran on his hands. When I saw him early in the race, I knew there was no way I could not finish. True hero? You bet.

"You should run your first marathon for the right reasons because you'll never be the same person again," said Bill Wenmark, my friend and marathon coach. "You must want to do it, not do it because your boss did it or your spouse did it."

Bill has trained 3,800 first-time students and only three have not finished the marathon. A dedicated Marine, Bill has run 103 marathons and is a world-class mountain biker at age 65.

The vast majority of people who sign up to run a marathon are not competing for prize money. They are in it to prove to themselves that they can do it. That thinking carries over into so many other parts of our lives.

To me, marathons are a metaphor for life. There are challenges, obstacles, rallies, accomplishments and celebrations. The finish line is a sweet sight for any competitor.

As Booker T. Washington said: "Success is measured not so much by the position that one has reached in life as by the obstacles which he has overcome while trying to succeed."

Mackay's Moral: If you don't climb the mountain, you can't see the view.

Napoleon Hill, one of my favorite authors, devoted 20 years of his life to studying what made people successful. His mentor, steel magnate Andrew Carnegie, helped Hill by introducing him to some of the most successful people in business, including Henry Ford, Theodore Roosevelt, Charles Schwab, George Eastman, John D. Rockefeller, Thomas Edison, Clarence Darrow and many others.

What Hill discovered is that all these individuals realized the importance of surrounding themselves with people smarter than they were.

I couldn't agree more. All of us together are a lot smarter than any one of us. Which leads to some of the best career advice I can give you: Networking is a skill you must develop.

If I had to name the single characteristic shared by all the truly successful people I've met over a lifetime, I'd say it is the ability to create and nurture a network of contacts. A network replaces the weakness of the individual with the strength of your network. You don't have to know everything as long as you know the people who do.

A network can enrich your life. It can help you help others. A network improves your job security. If you build a network, you will have a bridge to wherever you want to go. So if you are ever up the proverbial creek, with a network you will always have a paddle.

Just remember, the more you exercise your networking muscles, the stronger they get and the easier networking becomes.

What other career advice can you benefit from?

You can't forget the most important five-letter word in business -- TRUST. How about integrity, reputation and treating everyone with respect? I might add that you have to continue your education, because you should be in school all your life. I've written extensively about all these topics, and will continue to hammer them home because they are the difference between a job and a successful career.

And because I follow my own advice and continually study the brilliant thoughts of others, I'll share words of wisdom from some of the world's most successful people:

Steve Jobs, co-founder of Apple Inc.: "When I was 17, I read a quote that went something like: 'If you live each day as if it was your last, someday you'll most certainly be right.' It made an impression on me, and since then, for the past 33 years, I have looked in the mirror every morning and asked myself: 'If today were the last day of my life, would I want to do what I am about to do today?' And whenever the answer has been 'no' for too many days in a row, I know I need to change something."

Michael Dell, founder of Dell Inc.: "Try never to be the smartest person in the room. And if you are, I suggest you invite smarter people, or find a different room."

J.K. Rowling, author of the Harry Potter novels: "Had I really succeeded at anything else, I might never have found the determination to succeed in the one arena I believed I truly belonged."

Carlos Slim Helu, telecommunications magnate who is considered the world's richest person: "I don't want to live thinking about how I'll be remembered."

Warren Buffett, chairman of Berkshire Hathaway: "I don't look to jump over 7-foot bars. I look around for 1-foot bars that I can step over."

Mark Zuckerberg, co-founder of Facebook: "If we want to have the biggest impact, the best way to do this is to make sure we always focus on solving the most important problems."

Cathie Black, former president of Hearst Magazines: "Most people see taking risks as opening themselves up to unnecessary, maybe even dangerous chances. But the truth is, avoiding risks won't keep you safe, nor will it guarantee a smooth ride at work or in life."

Richard Branson, founder and chairman of Virgin Group: "My mother always taught me never to look back in regret but to move on to the next thing. The amount of time people waste dwelling on failures rather than putting that energy into another project, always amazes me. ... A setback is never a bad experience, just a learning curve."

Mackay's Moral: They say a word to the wise is sufficient, but I say a word from the wise is a gift!

One of life's great annoyances is the tendency of folks to ask you to perform an impossible task, list the issues they foresee and the problems that have plagued previous attempts -- and then admonish you to "think positive."

Wow! Does that mean you are so good that you can achieve what no one else has? Or are you being set up to fail?

Because I am an eternal optimist, I prefer to believe the first premise. Positive thinking is more than just a tagline. It changes the way we behave. And I firmly believe that when I am positive, it not only makes me better, but it also makes those around me better. I think that good attitudes are contagious. I want to start an epidemic!

A friend who also prefers to look for the silver lining suggested I Google "The Positive Pledge" by author and inspirational speaker Jon Gordon. Several promises stand out among the 15 in the pledge, including:

-- I pledge to be a positive person and positive influence on my family, friends, co-workers and community.

-- I vow to stay positive in the face of negativity.

-- When I want to be bitter, I will choose to get better.

-- When I meet failure, I will fail forward, toward future success.

-- I believe my best days are ahead of me, not behind me.

The full pledge is a terrific framework for a positive attitude because we know that positive thinking isn't always easy. Negative thoughts can creep into our minds -- and jump out our mouths -- when we least expect them. The trick isn't to fight them, but to manage them so they don't paralyze us.

Identify the triggers. When you have a negative thought ("This will never work ... I can't do this"), stop and ask yourself what's bringing it on. You may be tired or stressed out, or you may be affected by someone else's perspective. If you can locate the cause, the thought itself won't have as much power over you.

Focus on the now. Worrying about the past or the future isn't productive. When you start chastising yourself for past mistakes, or seeing disaster around every corner, stop and take a breath and ask yourself what you can do right now to succeed. Find something to distract you from destructive thoughts and reset your attitude.

Replace the negative. If you find yourself plagued by a recurrent worry, train yourself to think of something else. Memorize a short poem, phrase or meditation, and when you catch yourself in a negative thought, replace the negative with the positive. Your conscious mind can concentrate on only one thought at a time, and driving the negativity away will free you up to move forward again.

Years ago, I came across an essay that really solidified my commitment to positive thinking. It has been credited to several people, most often Robert J. Burdette or the ubiquitous "unknown." Regardless of who authored it, here is the message for you to contemplate:

"There are two days in every week about which we should not worry, two days which should be kept from fear and apprehension.

"One of these days is Yesterday with its mistakes and cares, its faults and blunders, its aches and pains. Yesterday has passed forever beyond our control. All the money in the world cannot bring back Yesterday. We cannot erase a single word we said. Yesterday is gone.

"The other day we should not worry about is Tomorrow with its possible adversities, its burdens, its large promise and poor performance. Tomorrow is also beyond our immediate control. Tomorrow's sun will rise. Until it does, we have no stake in Tomorrow, for it is yet unborn.

"This leaves only one day -- Today. Anyone can fight the battles of just one day. It is only when you and I add the burdens of those two awful eternities -- Yesterday and Tomorrow -- that we break down.

"It is not the experience of Today that drives men mad. It is remorse or bitterness for something that happened Yesterday and the dread of what will happen Tomorrow."

That's a difficult formula to improve upon, and perhaps even more challenging to practice. But I promise you, I'm positive you will be better off for trying!

Mackay's Moral: A positive attitude lightens your load and expands your reach.