When we start being too impressed by the results of our work, we slowly come to the erroneous conviction that life is one large scoreboard where someone is listing the points to measure our worth. And before we are fully aware of it, we have sold our soul to the many grade-givers. That means we are not only in the world, but also of the world. Then we become what the world makes us. We are intelligent because someone gives us a high grade. We are helpful because someone says thanks. We are likable because someone likes us. And we are important because someone considers us indispensable. In short, we are worthwhile because we have successes. And the more we allow our accomplishments — the results of our actions — to become the criteria of our self-esteem, the more we are going to walk on our mental and spiritual toes, never sure if we will be able to live up to the expectations which we created by our last successes. In many people's lives, there is a nearly diabolic chain in which their anxieties grow according to their successes. This dark power has driven many of the greatest artists into self-destruction. 

Henri Nouwen