Protestant Reformers, upholding the doctrine of justification by faith, held that repentance consisted in a change of the whole moral attitude of the mind and soul (Matthew 13:15; Luke 22:32), and that the divine forgiveness preceded true repentance and confession to God without any reparation of "works". Rather, "God's kindness is meant to lead you to repentance" (Romans 2:4, ESV). In his Of Justification By Faith, Calvin says: "without forgiveness no man is pleasing to God." Nonetheless, in traditions formed by a Calvinist or Zwinglian sensibility there has traditionally been a stress on reconciliation as a precondition to fellowship.
The attitude of penance or repentance can be externalized in acts that a believer imposes on himself or herself, acts that are themselves called penances. Penitential activity is particularly common during the season of Lent and Holy Week. In some cultural traditions, this week, which commemorates the Passion of Christ, may be marked by penances that include flagellantism or even voluntary pseudo-crucifixion. Advent is another season during which, to a lesser extent, penances are performed. Acts of self-discipline are used as tokens of repentance. Easier acts of self-discipline include devoting time to prayer or reading of the Bible or other spiritual books. Examples of harder acts of self-discipline are fasting, continence, abstaining from alcohol or tobacco, or other privations. Self-flagellation and the wearing of a cilice are more rarely used. Such acts have sometimes been called mortification of the flesh, a phrase inspired by Romans 8:13: "If you live according to the flesh you will die, but if by the Spirit you put to death the deeds of the body, you will live."
Such acts are associated also with the sacrament. In early Christianity, public penance was imposed on penitents, the severity of which varied according to the seriousness of the offences forgiven. Today the act of penance or satisfaction imposed in connection with the sacrament for the same therapeutic purpose can be set prayers or a certain number of prostrations or an act or omission intended to reinforce what is positive in the penitent's behaviour or to inhibit what is negative. The act imposed is itself called a penance or epitemia.
In the Eastern Orthodox Church, penance is usually called Sacred Mystery of Confession. In Orthodoxy, the intention of the sacramental mystery of Holy Confession is to provide reconciliation with God through means of healing.
Similar to the Eastern Catholic Churches, in the Eastern Orthodox Church there are no confessionals. Traditionally the penitent stands or kneels before either the Icon of Christ the Teacher (to the viewers' right of the Royal Door) or in front of an Icon of Christ, "Not Made by Hands". This is because in Orthodox sacramental theology, confession is not made to the priest, but to Christ; the priest being there as a witness, friend and advisor. On an analogion in front of the penitent has been placed a Gospel Book and a Crucifix. The penitent venerates the Gospel Book and the cross and kneels. This is to show humility before the whole church and before Christ. Once they are ready to start, the priest says, “Blessed is our God, always, now and ever, and unto the ages of ages,” reads the Trisagion Prayers and the Psalm 50 (in the Septuagint; in the KJV this is Psalm 51).