This text indicates that the joy of the Christian is not the natural joy of human life. It is a supernatural joy insofar as it has a supernatural source. It is the work of Christ within us. Though Jesus spoke of His joy being in us, it is still our joy once it is in us. He is its source and its power, but it is still our joy.
Jesus also spoke of the end or purpose of His joy remaining in us, namely, that our joy may be full. The term full speaks of a degree, in this case an ultimate degree. There is no more joy than full joy. Yet we can experience partial joy or less than full joy, not because there are fluctuations in Jesus’ joy, but because there are fluctuations in the degree of our abiding in Christ.
We cannot fall out of Christ, but in the process of sanctification we experience greater and/or lesser degrees of clinging closely to Him. Here our wills are important in that we are called to abide in Christ.
Coram Deo: Ask God for supernatural joy to flood your life.
Passages for Further Study
Isaiah 61:1, 3