Joy is essential to spiritual life. Whatever we may think or say about God, when we are not joyful, our thoughts and words cannot bear fruit. Jesus reveals to us God's love so that his joy may become ours and that our joy may become complete. Joy is the experience of knowing that you are unconditionally love and that nothing — sickness, failure, emotional distress, oppression, war, or even death — can take that love away.
Joy is not the same as happiness. We can be unhappy about many things, but joy can still be there because it comes from the knowledge of God's love for us. We are inclined to think that when we are sad we cannot be glad, but in the life of a God-centered person, sorrow and joy can exist together. That isn't easy to understand, but when we think about some of our deepest life experiences, such as being present at the birth of a child or the death of a friend, great sorrow and great joy are often seen to be parts of the same experience. Often we discover the joy in the midst of the sorrow. I remember the most painful times in my life as times in which I became aware of a spiritual reality much larger than myself, a reality that allowed me to live the pain with hope. I dare even to say: "My grief was the place where I found my joy." Still, nothing happens automatically in the spiritual life. Joy does not simply happen to us. We have to choose joy and keep choosing it every day. It is a choice based on the knowledge that we belong to God and have found in God our refuge and our safety and that nothing, not even death, can take God away from us.— Henri J. M. Nouwen, The Heart of Henri Nouwen by Rebecca Laird, editor, Michael J. Christensen, editor