The Sacrament of Reconciliation is one of the least used and often most misunderstood sacraments of the Catholic Church. It is the visible sign by which one can see the mercy of God at work in the world. What most see as a place of shame is a place of victory. Coming to Confession means you have not given up on becoming the person that Christ has created you to be. Confession is an opportunity to not only admit our sins but also to receive the grace necessary to avoid sin in the future. It is how the Church lives out Christ's command to forgive sins, and it is through His authority that the Priest gives us absolution.
The Sacred Scriptures record that "Jesus said to them again, 'Peace be with you. As the Father has sent me, even so, I send you.' And when he had said this, he breathed on them, and said to them, 'Receive the Holy Spirit. If you forgive the sins of any, they are forgiven; if you retain the sins of any, they are retained'" (John 20:21-23). This is the very essence of what Confession is. It is an opportunity to encounter Christ face to face in repentance, receive penance, and go forth with your sins forgiven.
To understand exactly why Confession looks today, it is necessary to know a little history of it. When the Church began, penance was a public affair. One had to get up before the entire congregation and Confession your sins in front of all of them. Then one had to spend time in public penance, often laying in the doorway of the Church as people walked over and around them. Public penance could last a few years. Finally, you may be readmitted to the crowd. This was unpopular, and since it was only allowed once in a lifetime, it was often put off until the deathbed.
"During the seventh century Irish missionaries, inspired by the Eastern monastic tradition, took to continental Europe the 'private' practice of penance, which does not require public and prolonged completion of penitential works before reconciliation with the Church. From that time on, the Sacrament has been performed in secret between penitent and priest" (CCC 1447). This is the Sacrament as we see it today. The Priest configured to Christ by Holy Ordination, represents not only Christ but also is a representative of the community. It is he, instead of the entire congregation, who hears the Confession and offers absolution. It is Jesus who hears the Confession and through the Priest extends to you the forgiveness of sin.
Knowing what we believe about the Holy Sacrament of the Altar, one should go to Confession any time they are aware of Mortal Sin. The Church also teaches that one should go to Confession at least once a year, during Easter. That is the bare minimum. Frequent Confession is a good idea!