The Key to Happiness by Brian Tracy

Your ability to achieve your own happiness is the key measure of your success, of how well you are doing as a person.You learn the key to happiness that has been the same through all of history. You learn how to dispel the two myths that may be holding you back and how to achieve more happiness in everything you do.

Dedicate Yourself to Your Best Talents
The key to happiness is this: dedicate yourself to the development of your natural talents and abilities by doing what you love to do, and doing it better and better in the service of a cause that is greater than yourself.This is a big statement and a big commitment. Being happy requires that you define your life in your own terms and then throw your whole heart into living your life to the fullest. In a way, happiness requires that you be perfectly selfish in order to develop yourself to a point where you can be unselfish for the rest of your life.