There is a quality of sadness that pervades all the moments of our life. It seems that there is no such thing as clear-cut pure joy, but that, even in the most happy moments of our existence, we sense a tinge of sadness. In every satisfaction, there is an awareness of its limitations. In every success, there is the fear of jealousy. Behind every smile, there is a tear. In every embrace, there is loneliness. In every friendship, distance. And in all forms of light, there is the knowledge of surrounding darkness.
—Henri Nouwen, Out of Solitude: Three Meditations on the Christian Life