Forgiveness of Sins

In my deep study of both Catholicism and Mormonism over the past year or so, one question that seems to keep coming up is: how can I know when I have been forgiven of sins? Latter-day Saints believe that we can know we have been forgiven of our sins when we have truly repented and we feel peace and joy through the Holy Ghost. Forgiveness comes only after repentance. (Repentance is a whole other topic in and of itself, perhaps for another blog post.) With Catholics, repentance is also a factor in forgiveness, but they also have the Sacrament of Reconciliation – confessing your sins to a priest and the priest pronouncing your absolution. The priest himself is not the one doing the forgiving, but he is acting on behalf of Jesus Christ and represents the Church. The struggle I'm having with the LDS view is whether feelings of peace and joy are a reliable sign that you have indeed been forgiven of sins. Can you feel like you've been forgiven when you really haven't? How can you know for…