Why do I have to confess to a priest? Isn't it enough to confess directly to God?
In the parable of the "Prodigal Son", we learn a great deal about confession. The priest is your spiritual father to whom has been assigned the task of monitoring your spiritual growth. Confession to the spiritual father is evident; for once the son repented of his sin and returned to his father confessing: "Father, I have sinned against heaven and in your sight..." (Luke 15:20-21), he had been forgiven and his place in the family (the church family) had been restored with celebration.
The priest has been given the authority from Jesus Christ our Lord, Himself, to bind and lose sins on earth; so that what is bound on earth will be so in heaven, and what is loosed on earth, will likewise be so in heaven: "So Jesus said to them [the disciples] again, 'Peace to you! As the Father has sent Me, I also 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 them; if you retain the sins of any they are retained'" (John 20:21-22).
When we confess to the priest, he will hold us accountable; he will give us spiritual direction and advice, pray for us, and support us in weakness or relapse. He will frequently check on us to see that we are committed and steadfast. Also since we are human, not only spirit, we need to hear: "your sins are forgiven, you are absolved. Go in peace." These words will relieve us from the consequences of sin (guilt, shame, and fear).