The meaning of fullfillment is deeply personal and very different for everyone. It may include some external measures of success such as a good job, money to live the lifestyle you choose, the home of your dreams or the car of your dreams. These are all elements of a fulfilling life and I relate to all of these. It's not only easy but possible to let the external measures drive our decisions.
However, I think there is a deeper level of fulfillment that comes from deep inside you. At some point in life, you realize that true fulfillment comes from your heart and soul. It's an inside out job. With this realization you begin to understand what truly has value in your life. When this happens you begin to view the choices in front of you with a different set of eyes. You make choices from your value perspective.
For example, if you value family, and you work 90 hours a week, what level of fulfillment do you have? If you value a creative and stimulating job, but you find yourself in a non-creative and routine job, what level of fulfillment do you have?
Identifying your values or what's important to you is a powerful step in living a fulfilling life. I challenge you to start the process now. Take one week and notice what is really important to you, write it down, notice what shows up, be curious and enjoy the process.