Gaudete Sunday, or Rose Sunday, in Advent. Gaudete means Rejoice.
Brothers and sisters: Rejoice always. Pray without ceasing. In all circumstances give thanks, for this is the will of God for you in Christ Jesus. Do not quench the Spirit. Do not despise prophetic utterances. Test everything; retain what is good. Refrain from every kind of evil. May the God of peace make you perfectly holy and may you entirely, spirit, soul, and body, be preserved blameless for the coming of our Lord Jesus Christ. The one who calls you is faithful, and he will also accomplish it. (I Thessalonians 5:16-24)
Rejoicing is an area in which I could use improvement. I remember a line from the song "L'chaim," in "Fiddler on the Roof": "God would like us to be joyful even when our hearts lie panting on the floor. How much more should we be joyful when there's really something to be joyful for."
Gaudete is the first Latin word of this passage from Philippians 4, which opens a Catholic mass on the third Sunday of Lent:
Rejoice in the Lord always. I will say it again: Rejoice! Let your gentleness be evident to all. The Lord is near. Do not be anxious about anything, but in everything, by prayer and petition, with thanksgiving, present your requests to God.
This is the Sunday when you light the rose-colored candle in the Advent wreath.