154 In the period of Advent, for instance, the Church arouses in us the consciousness of the sins we have had the misfortune to commit, and urges us, by restraining our desires and practicing voluntary mortification of the body, to recollect ourselves in meditation, and experience a longing desire to return to God who alone can free us by His grace from the stain of sin and from its evil consequences.
Source: Mediator Dei (Vatican.va)