Why Ambitiousness?

In a world where ambition is sometimes frowned upon, why would I explicitly focus on such a habit and more so, consider it a virtue?  I agree with Ayn Rand's definition of ambition: "the systematic pursuit of achievement and of constant improvement in respect to one’s goal" By this conception, hopefully you can envision a positive aspect to ambition.  I want to improve my understanding of the world.  I want to improve the education program at my school.  I want to improve my family's financial situation.  I want to improve my productivity.  I want to improve my ability to communicate effectively.  I want to improve my relationship with my wife and family.

It is imperative to have and pursue goals in order to stay alive.  When these goals are rationally based in reality, we have the framework for developing these goals towards higher and higher achievements that are fulfilling and meaningful.  I could not and would not be satisfied with my current income level for the rest of my life - not because I am not making enough to enjoy life, but because I would be a sign that my life has become stagnate.  Once I achieve today's goals, I set my bar higher to achieve tomorrow's goals.  As I continually push myself to be the best that I can be, I increase my enjoyment of life.  If I am a better professor, my students and colleagues should hopefully respond positively.  If I find ways to increase my income, I will be able to experience better life's wonders or prepare myself better for emergencies.  If I am a better husband, I will have a more fulfilling relationship with my wife.  If I am a better father, my children will have a better chance at becoming fully independent, virtuous, happy adults.

When ambition turns to irrational goals (political power, prestige, etc.), the dark side of ambition rears its ugly head.  I have no desire for power over others nor care about my prestige because neither of these things will improve my happiness.  Nor should anyone.