Catholics typically say the Act of Contrition after receiving the sacrament of Reconciliation; they may also say the prayer as part of their regular evening devotions. Believers can pray the Act of Contrition daily to ask for forgiveness for any sins they may have committed that day.
Catholics believe there are two different kinds of contrition: perfect and imperfect. Perfect contrition describes true sorrow over committing sin, while imperfect contrition denotes regret for sin that stems from the fear of God's punishment. The standard Act of Contrition expresses both perfect and imperfect contrition. The prayer ends with the believer's resolution to confess sins, perform penance to atone for sin and to try to avoid sinful behavior going forward. There are a few different versions of this prayer; however, each Act of Contrition offers apologies to God and resolves to try to avoid sin in the future.
Even if a Catholic prays an Act of Contrition each night, it does not obviate the need for regular confession. To receive the sacrament of Reconciliation, a Catholic confesses his sins to a priest, is given penance and receives absolution. A Catholic can prepare for Reconciliation by first examining her conscience; she can use the Ten Commandments as a starting point, questioning whether she has broken any Commandments through her thoughts or actions. By being aware of her sin in this way, she can make her Act of Contrition more mindfully. According to the Catechism of the Catholic Church, this type of interior change and growth is more important than exterior displays, such as fasting; without a change of heart and true contrition, outward acts of repentance are meaningless.