People see the world the way they want to see it. Its called their worldview. It may not be the way the world actually is. It usually isn't. It is influenced by their ambitions, desires, hopes and daydreams.
Their daydreams are often an idea of what they would like the world to become. Its a future worldview. Again, not usually based in reality. To accomplish those daydreams, they set goals. They figure that if they want it bad enough and set goals to achieve it, they can change the real world to fit the future worldview they have created. Since these goals are based on a biased view of the world and an unrealistic idea of the future these goals are destined for failure.
William Hung of American Idol fame wanted to be a pop star singer. That was his worldview. Reality (Simon Cowell) says otherwise. I give the guy credit for trying, but the reality is, he will make a better Civil Engineer than a pop star.
When setting goals, we must step outside our worldview and face the reality of the situation. Goals should be based on realities and not on wants or needs. Just because you want your product to grow 15% year over year doesn't mean the market can bear it.
This isn't to say you shouldn't dream. Dreams are great. Dreams are important. But Daydreams can lead you astray when setting goals for real life situations. Daydreams may even make you miss out on real opportunities because you were too busy hoping for something else. What if William is so focused on being a pop star that he never pursues engineering?
I've just worked with a lot of people who set unattainable goals because they never stepped outside their worldviews long enough to figure out if their goals were realistic. When they fail to meet their goals, upper management isn't happy. They are unhappy. And the campaign seems like a failure.
Its a difficult balance. I am sure what seemed like possible reality to the Wright brothers seemed like a Daydream to everyone else. The trick is to find the balance between what is a dream that is actually possible and what is a dream in which you are hoping to alter reality to fit your worldview.