In their 1966 Pastoral Statement on Penance and Abstience, the U.S. Bishops noted that changing customs around Christmas had diminished the appreciation for and understanding of Advent (#5). They noted that some Christians had tried to restore the spirit of Advent by recomitting themselves to the austerities of traditional Advent. "Perhaps their devout purpose will be better accomplished, and the point of Advent will be better fostered if we rely on the liturgical renewal and the new emphasis on the liturgy to restore its deeper understanding as a season of effective preparation for the mystery of the Nativity" (#6).
The Bishops went on to encourage Catholics to meditate on the lessons of the liturgy and to participate in the liturgical rites of Advent (#7). They also suggest that "If...liturgical observances are practiced with fresh fervor and fidelity to the penitential spirit of the liturgy, then Advent will again come into its own" (#8).
The section on Advent concludes with the Bishops saying that they are "counting on the liturgical renewal of ourselves and our people to provide for our spiritual obligations with respect to this season" (#9).
Now that it is 43 years later, I think we can examine this text and see that it was counting on too much. For one thing, of course, it is somewhat vague on the Advent practices that ought to be adopted by the people. Are they just supposed to "try harder" at Mass now that it's in English? Are all families supposed to have an Advent wreath? And why the judgment against those who engage in penitential practices during Advent?
When I read this section four decades later, it seems to me that what happened here was an attempt at replacement. They wanted to replace practices of the virtue of penance with "liturgical renewal." Or maybe we could say that they thought since the people would now understand Advent liturgies, Advent would be more meaningful to them, and they would have no need of those penitential practices that reminded them daily that it was Advent.
I'm a big fan of liturgy, so don't get me wrong. But considering that most Catholics participate in only five liturgies in the season of Advent (four Sundays plus the Immaculate Conception), it seems a little pollyanish to think that the liturgy by itself will be effective preparation for Christmas. Undeniably, there is great grace in the Eucharist regardless. And yet the Eucharistic training or liturgical training of the Mass only "comes into its own" when it is tied into a network of practices. This is true year-round, but it is especially true in those special seasons of the year - Advent, Christmas, Lent, and Easter. Something has to mark these seasons in the everyday.
Most Catholics are aware that Lent is a penitential season; we make our little Lenten sacrifices or "fasts." We might add a special time of prayer or give alms. We make a special effort to get to the sacrament of confession. But few Catholics have any association with Advent as a penitential season. One sign of this disconnect is the common change of liturgical colors, from purple to blue. Advent is meant to be purple, identifying it with Lent as a time of special preparation and penance. Churches nowadays seem to favor blue, to make it clear that Advent is NOT Lent. This might be a case of "liturgical renewal" gone awry. Replacing the penitential practices of Advent with an increased emphasis on the liturgy was not a fair trade. It not only removed the everday markers of the season, it made the season evolve into something entirely different, as indicated by the new colors.
Advent is a season of longing - longing for light, for warmth, for the entry of Christ into the world and the coming of Christ at the end of the world. There are many ways to mark this longing. We have our Advent wreath and our Advent calendars, for example. But there are other ways that we can make this longing felt, namely, by acts of penance, similar, though perhaps less intense, to those that we do during Lent. Because, while it is easy to SAY that we OUGHT to feel longing for Christ during Advent, if we don't change our habits during this season, we are unlikely to feel that longing, especially while we are surrounded by Christmas songs, Christmas lights, Christmas decorations, Christmas parties, and Christmas shopping.
During this season of Advent, we are called to recognize our sins and how they separate us from God. This is part of our longing for our Redeemer and Savior; we realize our own humanity and our need for God. By engaging in penance, we use our sins as an opportunity to grow closer to God, an opportunity to accept God's mercy and forgiveness. We prepare ourselves to accept the great gift God gives us - the gift of his Son.
Both worship and penance are species of the virtue of justice. By worshiping God in the Mass, we give God his due. By seeking to make amends for our offenses against God, we are giving God his due. We are called to both penance and worship. Acts of these virtues train us - not only in performing justice - but in receiving God's grace.