Today is known as Gaudete Sunday. The term Gaudete refers to the first word of the Entrance Antiphon, "Rejoice". Rose vestments are worn to emphasize our joy that Christmas is near, and we also light the rose candle on our Advent wreath.
In today's Gospel, John the Baptist appears to us as a figure of great humility.  Although his austere approach to the abandonment of worldly pleasures is not mentioned here in John's Gospel, his willingness to deny himself when courted with the temptation to embrace recognition and acclaim is clearly a profound expression of humility.  When confronted with the question "Who are you?" it would have been quite understandable for the Baptist to say something like, "I am the leader of a great spiritual revolution in the land."  Instead he professes himself to be unworthy to perform the task of untying the sandals of the one who is to come after him.
We are to learn from John the virtue of joy.  He was very much satisfied to take on the role of a precursor, of one who prepares the way and then steps aside for another to take over.  In our world today such a figure is vital.  If we seek to store up glory for ourselves in order to win the praise and attention of others, we miss the attitude of humility that leads to true joy.