Repentance
The main content of the Old Testament is summed up in the message of John the Baptist: Repent! There is no access to Jesus without the Baptist. One cannot come to Jesus without answering the plea of the precursor. Indeed, Jesus took up John’s message in summing up his own preaching: Repent and believe in the gospel! (Mk 1: 15).
The Greek word for repentance means: rethink; challenge your own and general way of life; let God enter into the criteria of your own life; do not live the way everyone else lives; do not do things the way everyone else does them; do not feel justified in doing dubious, ambiguous or bad things because others do the same; begin by seeing your own life with the eyes of God; seek that which is good, even if it is uncomfortable; do not base yourself on the judgement of the many, but instead on the judgement of God; in other words: seek a new lifestyle, a new life.
imago
Sign of conversion and penitence: the rite of ashes on Ash Wednesday. Pictured: Cardinal Angelo Comastri puts ashes on Pope Benedict’s head, 12 May 2013. The Mass, attended by numerous bishops and cardinals, was Benedict’s last major liturgical celebration before he resigned as Pope.
All this does not imply a moralism; those who reduce Christianity to morality, lose sight of the nature of Christ’s message, namely the gift of new friendship, the gift of the companionship with Jesus and therefore also with God. Those who convert to Christ do not intend on establishing their own moral independence; they do not claim to build up their own goodness by their own strength. “Conversion” (metanoia) means exactly the opposite: breaking out from self-sufficiency, recognizing and accepting one’s own neediness, the dependency on others and on the entirely Other, the dependency on his forgiveness, on his friendship. The unconverted life is self-righteousness (I am no worse than others). Conversion is the humility of entrusting oneself to the love of the entirely Other; a love that becomes the measure and guide of my own life.
The New Evangelization, in: Joseph Ratzinger Collected Works 8, ed. by Gerhard Ludwig Müller, Freiburg 2010, 1231–1242, here 1232 f. (German edition)