How can our Joy be complete as is asserted by Jesus in John 15:11? We were encourraged to think of God continuing his daily work in us, developing a people for himself, and that as Jesus sees that, his desire is to join in. This process gives Joy to both Jesus and God. And hopefully, as we realise that God and Christ have great joy in us - joy enough to make them sing over us, we will be inspired to share that Joy with other people, bring that joy into other people's lives.
John 15 also talks about pruning and trimming which is part of the process to stimulate growth and more joy.