The Priest has been given the power by God to forgive you for the sins that you have committed and of voiding any future consequences of those sins.
Confess your faults one to another, and pray one for another, that ye may be healed. The effectual fervent prayer of a righteous man availeth much. James 5:16
and be ye kind one to another, tenderhearted, forgiving one another, even as God for Christ’s sake hath forgiven you. Ephesians 4:16
forbearing one another and forgiving one another if any man have a quarrel against another: even as Christ forgave you, so also do ye. Colossians 3:13
Verily I say unto you, whatsoever ye shall bind on earth shall be bound in Heaven; and so whatsoever ye shall loose on earth shall be loosed in Heaven. Matthew 18:18