Read Luke 2:8-20.
What is joy? The emotion evoked by well-being, success, or good fortune or by the prospect of possessing what one desires (Merriam-Webster). The definition of joy as used in the Bible is closely related to gladness and happiness, although joy is more a state of being than an emotion.
The world tells us that joy comes from something within you, something you do. In other words, you alone are responsible for your joy. However, the true joy that God wants us to experience is not found within yourself.
The true joy that God wants us to experience in life is actually a gift. No, not the kind you find wrapped in fancy paper and placed under the Christmas tree. This gift was wrapped in swaddling clothes and placed in a manger.
The joy of God came to focus in human history and became individually available to us in Jesus Christ. The theme of joy runs through the entire biblical account of the coming of Christ. The most familiar passage is the angel’s announcement (Luke 2:10-11).

Joy is both a gift of God as well as a response to the gift of God.

True joy is not something I can produce with my own resources. It is a gift of God. That gift that offers great joy is the gift of His Son, Jesus.
Luke 2:11 states “as Savior has been born to you.” The English word “to” is implies action, a movement toward a place, person, or thing. It also is used to indicate contact or close proximity. This sounds a lot like the process of giving a gift to someone. You move the gift in their direction (an action) and it needs to be within their reach (close proximity). That is exactly what God did for us when He gave the gift of His Son.
Joy isn’t something you earn, deserve, or conjure up. Joy is a gift of God given to everyone who will receive it in all its simplicity.
Joy is also the response to the gift of God. When we believe in Christ, accept Him as the Savior of our sins, and choose to follow Him as Lord we will have joy.
Joy is defined as possessing what one desires (Webster). Placed within each of our hearts is a desire for relation with our Creator. That relationship is now only made possible through Christ Jesus — our Savior and Lord. When we choose to accept Christ as Savior of our sins and Lord of our life, we will find true and lasting joy — we possess that which we truly desire.

The Apostle Peter explains the joy of our salvation in Christ in his first letter. See 1 Peter 1:8-9.
Joy does not come from what you do — it comes from what Christ has done for you. Joy does not come from the right set of circumstances — it comes from trusting in Christ regardless of our circumstances.
Joy is both a gift of God as well as a response to the gift of God — Jesus Christ.
Jesus speaks of the joy He gives in one of his last moments with His disciples before He was arrested, beaten, and crucified. See John 15:9-11.
Is your joy complete today? It can be. But it won’t be completed by trying harder, acting happier, or thinking happier. It won’t be completed with the next purchase, experience, or event.

Joy is found in receiving God’s greatest gift of all, Jesus our Savior.