“I bring you good tidings of great joy.”

Luke 2:10 KJV
   And the angel said unto them, Fear not: for, behold, I bring you good tidings of great joy,
 which shall be to all people.

The above setting is the announcement of the birth of Jesus Christ by the angelica host.

“Joy to the world”

Joy is not fun; sometime we confuse joy with fun. Fun is passive or measured in the
excitement of the moment. Joy is a consent abiding state of being.

One cannot have fun when things are not going well, however that is not the case with joy.
There may be a time of storm in one’s life, yet the joy still remains.

We are told that in the eye of a Toronto there is calm, although there is turmoil all around
there is peace in the center or eye of the whirlwind.
So it is with joy, some time when we are tried and tested we still have the joy of the Lord.

Isaiah speaks of it as drawing of water from the wells of salvation. See: Isaiah 12:3.

“Believing, ye rejoice with joy unspeakable and full of glory:”

Here Peter as well as Isaiah, speaks of the joy of knowing Jesus Christ the Son of God,
as out personal savior, which brings great joy to the believer.

1 Peter 1:8 KJV
   Whom having not seen, ye love; in whom, though now ye see him not, yet believing,
ye rejoice with joy unspeakable and full of glory:

“The joy of the Lord is my strength!”