The hymn that we so often associate with Christmas was first sung as a millenial song by the early saints of the church as a hymn of a time when Christ will one day return to the earth. The hymn sang, Joy to the world, the Lord will come. Let earth receive her King. Let every heart prepare Him room. And saints and angels sing."
Alma 5:50 tells us about the time when Christ will return. "Yea, thus saith the Spirit: Repent, all ye ends of the earth, for the kingdom of heaven is soon at hand; yea, the Son of God cometh in his glory, in his might, majesty, power, and dominion. Yea, my beloved brethren, I say unto you, that the Spirit saith: Behold the glory of the King of all the earth; and also the King of heaven shall very soon shine forth among all the children of men.
Psalm 98:4-9 gives us direction on how we should act as we anticipate the return of our Savior. "Make a joyful noise unto the Lord, all the earth: make a loud noise, and rejoice, and sing praise. Sing unto the Lord with the harp; with the harp, and the voice of a psalm. With trumpets and sound of cornet make a joyful noise before the Lord, the King. Let the sea roar, and the fulness thereof; the world, and they that dwell therein. Let the floods clap their hands: let the hills be joyful together. Before the Lord; for he cometh to judge the earth: with righteousness shall he judge the world, and the people with equity."
There is no way you can sing Joy to the World without being filled with happiness and joy. I know that the Savior will come again into this world to rule and reign in glory and that it will be a most joyous occasion for those who are prepared to welcom Him.