The seed of faith is wrapped up into the greatest gifts of all. Even when I feel I have no joy or longing for God, the longing for the longing is a joy itself. If I don't have the longing, I have the sadness that I don't long. Thank God for this gift that will not let us go. Stop and take wonder. Let this properly build a confidence.
First, I would say that a Christian, no matter how dark the season of his sadness, never is completely without joy in God. I mean that there remains in his heart the seed of joy in the form, perhaps, of only a remembered taste of goodness and an unwillingness to let the goodness go. This is not the "joy that is inexpressible and filled with glory" ( 1 Pet. 1:8). It's not the joy that we have known at times and fight to regain. But it is a fragment of such joy—like a man who sits in prison and pulls out a tattered picture of his wife, or a paralyzed victim of a car accident who watches a video of the day he could dance. Or, even more fragmentary, the joy may only lie there in the cellar of our soul in the form of penitent sadness that we cannot desire God as we ought. Inside that sadness is the seed of what we once knew of joy. 1