All of the sacraments have been traditionally examined according to the form, matter, minister, and recipient necessary in order for them to be celebrated. Let’s use the Eucharist as an example. For a valid Eucharist to be confected, one needs an ordained priest or bishop (minister) to consecrate bread and wine (matter) by reciting an ecclesiastically approved Eucharistic prayer (form). In the celebration of this sacrament a recipient is not necessary for the Eucharist to be valid, however, if any of the other elements are lacking, then there is no Eucharist; if they are, it is merely bread and wine. Now, in the sacrament of Reconciliation, one needs a penitent (recipient) to be contrite of heart (matter) in confessing his/her sins, and have the words of absolution (form) spoken by a priest or bishop (minister). If any of these elements are lacking, there is no sacrament (see here); you’re simply having a meeting with a priest in a box. Further, I think it would be pastorally insensitive not to inform the penitent who lacks contrition of its necessity for the celebration of the sacrament. Otherwise, he or she may be under the false impression that his or her sins have been forgiven when, in point of theological – and canonical (see canon 987) – fact, they have not.
Secondly, the need for repentance is at the core of Jesus’ own message, his kerygma. “‘The Kingdom of God is at hand. Repent, and believe in the gospel’” (Mk 1:14-15; see Mt 4:17). During Ash Wednesday’s Mass, a portion of this passage is one of two that one might hear when receiving ashes; the other being: “Remember that ‘you are dust and to dust you shall return’” (Gen 3:19). It is a somewhat traditional English translation to render the word “repent” in the verse from the Mark’s Gospel for the original Greek word “metanoeite,” but the Greek word has a much richer meaning. It is a combination of the words “mind” [nous] and “beyond” [meta], and one could interpret this word rather physically as meaning: “take your head and turn it 180 degrees.” In one sense, a better English word than “repentance” is “conversion.” What we remember on Ash Wednesday is that Christ calls us to himself, to live in communion with him, and that this communion requires being attuned to him in heart, soul, and mind (cf. Lk 10:27; Dt 6:5). In short, on Ash Wednesday, Christ calls us to “return to [him] with [our] whole heart” (Jl 1:12).