When I was a child, one of my favorite stories was “The Little Engine That Could.” Allegedly, after each of the umpteen times I heard the story, I used to act like the little engine and chug around the house, saying, “I think I can. I think I can. I think I can.” This account was related to me by my mother—so it may be somewhat exaggerated for the sake of cuteness.

“The Little Engine That Could” was my first encounter with literature devoted to promoting a positive mental attitude. Although I haven’t done any chugging since I graduated from college, I still think of that story whenever I’m faced with a difficult situation or daunting task.

Developing and maintaining a positive mental attitude (or PMA, as it is often called in today’s personal-development lingo) has always been a secret for achieving success in life. In the book of Psalms, the Bible reminds us: “This is the day the Lord has made; let us rejoice and be glad in it.” Aesop’s fable “The Tortoise and the Hare” teaches that cockiness and raw ability are no match for conviction and perseverance. Through the ages, responsible parents have taught their children the value of cheerfulness, confidence, enthusiasm and expectancy.

Studying the effects of an optimistic outlook on life really came into its own as a behavioral science in the first half of the 20th century. Writers such as Napoleon Hill, Dale Carnegie and Norman Vincent Peale capitalized on this growing awareness of the power of positive thinking. Their books, Think and Grow Rich, How to Stop Worrying and Start Living and The Power of Positive Thinking, respectively, helped my parents’ generation to rethink life’s possibilities and believe that they could make their dreams come true.

Who knows? We baby boomers may actually be the product of a whopping dose of good ol’ PMA.

Hill, Carnegie, Peale and other pioneers in positive thinking also provided much of the conceptual foundation for today’s plethora of personal-development and business-enhancement books, tapes and seminars. Just about everyone you know has read or heard one self-help guru or another expound on the importance of PMA (although they rarely call it that).

Sadly, many pop psychologists disparage the concept of a positive mental attitude as being too simplistic. Without question, a pretentiously sunny disposition can be as irritating as a smiley face sticker slapped on your car’s windshield or an obsequious salesperson chirping “Have a nice day!” And most certainly, there are events in our live that call for a somber, introspective viewpoint. A smile may be your umbrella, but sometimes you need a raincoat and galoshes, too.

Nevertheless, nurturing a positive mental attitude toward life and letting that mindset mediate your behavior at home and at work can make a big difference in the quality of your life and the way you effect the lives of others. It is especially important to display a PMA in the workplace, particularly if you are in a position of leadership.

Much of what happens during an ordinary day at work is a product of communication. Too often, we think of communication only in terms of what we say. We forget that our tone of voice, gestures and body language also convey powerful messages that reflect our state of mind—sometimes better than our words do.

If you wish to develop and display a positive mental attitude, both the words you say and your demeanor should reflect a cheerful, confident, enthusiastic and expectant frame of mind. If you’re a griper, grouch or gloom-monger, you can count on colleagues and customers to notice your attitude and judge you and your business accordingly.

A PMA precedes success, rather than follows it. Earl Nightingale, another star in the constellation of great personal development teachers, once said, “Meeting a successful, happy person, people frequently make the mistake of saying, ‘I’d be happy too, if I had what he’s got.’ It’s perhaps natural to think his attitude is the result of his success, but just the reverse is true.”

Nightingale asserts that we attract the kind of life that matches our outlook on life. Before we can achieve something, he says, we must first become the kind of person that “something” would naturally belong to.

American psychologist and philosopher William James wrote: “The greatest discovery of my generation is that people can alter their lives by altering their attitudes of mind.” If you want to make a good impression on others, motivate the people you lead and metamorphose your life into a monument to success and satisfaction, start by taking a lesson from “The Little Engine That Could.” Tell yourself I think I can. I think I can. I think I can—until you do.