Before we can measure success, we must define it. Most definitions provided here, though commendable, I don't believe define or provide a means to measure success. They rather provide means to be happy and live purposefully. While I believe happiness and sense of purpose should constitute success, this isn't always the case. The best definition of success that I've heard is by Earl Nightingale. "Success is the progressive realization of a worthy goal or ideal." In other words, success lies not in the achievement of a goal, but in working towards one. And the goal, by this definition, must be something worthy. Based on this definition, a person is successful so long as he is working towards something worthy. A person could be successful yet miserable and unhappy, though this isn't the way one would want to be.