I was in Washington, D.C. the other day and struck up a conversation with a cab driver from Ethiopia. He beamed as he told me he had recently become a U.S. citizen. “This is my country,” he said proudly. And then he told me his story. He came to America eight years ago. He had no money. He had no family, no job, no education. The only thing he had was a little halting English to get around.

Since arriving, he’s been knocking down barriers. Here’s the shocker. He turned to me and said, “I just earned my degree from the University of the District of Columbia.” Turns out he’s been banging out one or two classes a semester at night and driving a cab during the day. He also got married and has a 2-year-old son.

I was stunned. Here he was driving one of those beat-up Crown Victoria taxis that should have been donated to the Kidney Foundation, working in the sweltering heat without good AC, driving around a lot of cranky people day after day — and this guy can’t stop smiling and he’s telling me America is his country.

Here’s some career counseling advice: Go ahead and have your children shadow people in different professions, take aptitude tests, talk to school counselors, assess career orientations and broaden their exposure to the world. But there’s something more important: Help them gain confidence in themselves and a vision of what's possible. That's the game-changer.

Every semi-skilled and unskilled person that I’ve met, assuming they are fully functional, is sitting on untapped potential. Admiral Hyman G. Rickover said, "Man has a large capacity for effort. In fact it is so much greater than we think it is that few ever reach this capacity.”

As you help your children and other young people choose a career, don’t worry so much about vocational options, at least not at first. Focus instead on helping them aim high. If young people gain confidence and vision, you won’t have to tell them to aim high. You may have to tell them to slow down and come back to earth.

Some people are born to advantage. Most are not. All the more reason to focus on what you can control. The biggest career limitations reside inside the person. Apathy is one thing, but a lack of confidence and vision is something else. You can help someone who lacks confidence and vision. Somewhere along the line, my Ethiopian friend got the idea that he could go to college. Too many of our young people still think they can’t handle college or some kind of post-secondary training. It’s simply not true. They just haven’t had enough personal triumphs to reveal the truth of their own potential.

The most important thing adults can do to help assist young people in their career development is to help them gain confidence and vision through earned achievement. This is leadership in its truest sense. Ronald A. Heifetz and Donald L. Laurie explain, “The leader’s most important role is to instill confidence in people.” Achieving small wins drip-feeds confidence over time.

When I was a student at the University of Oxford, I sat for my final exam after five years of study. I thought it would be little more than a formality because I had met the degree requirements. Later that evening, I walked out of Nuffield College into the dreary English weather. I found a phone booth on the street and called me wife who was back in the states to inform her that I had failed the exam. That was not part of the plan. I was shattered.

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Fortunately, my wife, who is also my coach, told me I could do it and so we got back to work. The Scottish politician Walter Elliot said, “Perseverance is not a long race; it is many short races one after the other.” I regained confidence and vision, and passed the second time. That success had little to do with raw intelligence and more to do with stamina. I think that's the story most of the time.

Confidence and vision supply the stamina and we become more willing to delay gratification for bigger rewards later.

Timothy R. Clark is the founder of TRClark LLC, a management consulting and leadership development organization. His newest book, "The Employee Engagement Mindset," has just been released from McGraw-Hill. Email: trclark@trclark.net