There is this wonderful story about an eagle that illustrates this point well. Once upon a time, there was a large mountainside, where an eagle's nest rested. The eagle's nest contained four large eagle eggs. One day an earthquake rocked the mountain causing one of the eggs to roll down the mountain, to a chicken farm, located in the valley below. The chickens knew that they must protect and care for the eagle's egg, so an old hen volunteered to nurture and raise the large egg.

One day, the egg hatched and a beautiful eagle was born. Sadly, however, the eagle was raised to be a chicken. Soon, the eagle believed he was nothing more than a chicken. The eagle loved his home and family, but his spirit cried out for more. While playing a game on the farm one day, the eagle looked to the skies above and noticed a group of mighty eagles soaring in the skies. "Oh," the eagle cried, "I wish I could soar like those birds." The chickens roared with laughter, "You cannot soar with those birds. You are a chicken and chickens do not soar."

The eagle continued staring, at his real family up above, dreaming that he could be with them. Each time the eagle would let his dreams be known, he was told it couldn't be done. That is what the eagle learned to believe. The eagle, after time, stopped dreaming and continued to live his life like a chicken. Finally, after a long life as a chicken, the eagle passed away.
The moral of the story: You become what you believe you are; so if you ever dream to become an eagle follow your dreams, not the words of a chicken.

How often do we let ourselves be defined by other people, we let them determine our self worth whether we realize it or not. In order to live your full potential you must first believe you were born to be more than you are, you must believe it with such conviction that you follow your dream no matter how often you may be ridiculed or how often you stumble. For it is in the act of following ones dreams that your potential will be realized.

The worst thing that could happen in life is to wake up one day and realize too late that we have been held back from our dreams because we were too afraid to lift ourselves out of the chicken pen and from the small thinking people whilst they may mean well can only see possibilities through their limitations and not from your possibilities.