Joy and faith go hand in hand. When we take shelter in the Rock of our salvation, with a quiet assurance in our hearts that He is in control, how can we not have joy?
Psalm 16:11 is a prayer, a praise and an affirmation of faith all rolled into one short verse.
Thou wilt shew me the path of life: in thy presence is fulness of joy; at thy right hand there are pleasures for evermore.
If our joy is lacking, it's not because God failed to supply it. He didn't go anywhere. He has promised to never leave us. If our joy is lacking, it's because we have failed to spend time with the Source of true joy.
Want joy? Spend time in His presence.