Your progression through Tang Soo Do must really be viewed not as a race to a certain goal, but rather as a journey through life. The various ranks that you may attain on this journey are simply milestone markers. While they are important in that they allow you to measure the progress that you have made in your journey, they are not the reason for the journey.
Likewise, while achieving the rank of Blackbelt is a tremendous accomplishment, it is not the reason for your journey; it is merely another milestone. If anything, it is the milsetone that signals the end of the beginning of your journey. Consider this: it takes longer to move from 1st Degree to 3rd Degree Blackbelt, than it does to move from novice beginner to 1st Degree Blackbelt. Attaining the rank of Blackbelt simply means that you have learned what is required to become a true martial artist - now you have to strive to become one.
A black belt is not the end of your journey; the journey never ends. The goal of the journey is to better yourself in all aspects of your life; personal, professional and spiritual. In effect, the goal of your journey is the journey itself.