When I was an Evangelical Protestant thinking about returning to the Catholic Church of my baptism, among Catholic practices I found difficult to accept was the sacrament of penance.
I thought that the sacrament took away from Christ’s sufficiency to forgive all our sins, past, present, and future. For I believed that it diminished the scope of Christ’s atonement if I had to do something in order to acquire forgiveness, such as confess to a priest and/or do penance, i.e., say some prayers, do a good deed, or engage in a spiritual discipline, after receiving absolution. But good reasons eventually led me to change my mind.
First, even Evangelical Protestants have a means for dealing with post-baptismal sin: the rededication. The backslider, depending on the severity of his iniquity, rededicates his life to Christ by walking the aisle once again, as he did when he first converted. In fact, given the Protestant understanding of justification and sanctification – that good works and good living follow from being truly saved – the backslider may wonder if his first confession was a sham. So, he confesses again. Thus, it became clear to me that Christianity requires some way to deal with post-baptismal sin.