John's epistle helps us to diagnose our spiritual health.

Your spiritual health (fullness of joy) is found in mutual fellowship with brothers and sisters in Christ who share life with the triune God, by faith in Jesus Christ.

I. You must know Christ personally in order to have any kind of spiritual health (1-2).

II. You must have a correct understanding of God in order to stay spiritually healthy (3)

III. Your spiritual health can be gauged by your joy (4)