According to Osho, joy originates in your being and flows outward through the heart, which is only a vehicle for its expression. As you deepen into being, the heart's channel becomes clearer, wider, and more radiant; joy does not drop, it intensifies. Centered in being, you don't have joy; you are joy, so drop attachment and imitation, and let it naturally express.
Joy comes from the deepest you and shines through your heart; get quiet inside and stop clinging or copying, and it will show by itself.