The secret to Christian joy is having a clean heart.
John wrote his first letter so that all who read it would have fellowship with them, and that fellowship is with the Father and the Son, and this fellowship is where the fullness of joy is. John explains that God is light and in Him there is no darkness at all. This means you can’t be in fellowship with the Light of God and hold on to any darkness. But the good news is that if you walk in the light and you let the Light expose your sins so that you can confess your sins and be forgiven, then we have fellowship with God and one another, and the blood of Jesus cleanses us from all sin.
So this is the secret to having Christian joy. The fullness of joy is being in fellowship with God, who is all light, all the time. In Him there is no darkness at all: there are no shadows. In the course of our lives there will be hardships, and we certainly sin, but those shadows cannot stick to us if we stay in the Light. Jesus says that the joy He gives is the kind of joy that no one can take away from you. This is because no one can take away your fellowship with God; no one can take away your clean heart.
But sometimes true Christians sin and their joy can be diminished. True Christian joy can never be lost, but if you aren’t confessing your sins, the joy of your salvation can become muffled. Your filters can get clogged. But if you confess your sins, God will restore to you the joy of your salvation, and with a clean heart, you will breathe the clean mountain air of God’s delight. If you confess your sins, He is faithful and just to forgive us and cleanse us from all unrighteousness.
Do you want Christian joy? Then confess your sins and get a clean heart.