The difference between shallow happiness and a deep, sustaining joy is sorrow. Happiness lives where sorrow is not. When sorrow arrives, happiness dies. It can’t stand pain. Joy, on the other hand, rises from sorrow and therefore can withstand all grief. Joy, by the grace of God, is the transfiguration of suffering into endurance, and of endurance into character, and of character into hope — and the hope that has become our joy does not (as happiness must for those who depend on it) disappoint us.
From Reliving the Passion: Meditations on the Suffering, Death, and Resurrection of Jesus as Recorded in Mark by Walter Wangerin, Jr.