Efficacy of Sacraments

The example of confession is good.

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 20:22-23

Where does Jesus say people have to go and confess their sins to have them forgiven? He spoke the above words instead. There are the other references to the apostles bidden to bind and loose.

How do these apostles forgive anybody's sins when they do not know what the sins are that they are forgiving, or for that matter, to which they are withholding forgiveness? Jesus gives them not the power of extending some kind of blanket-forgiveness, overriding their wills, but, in complete trust, also of withholding that forgiveness. On what grounds are they to withhold? Well, if the person seeking the obliteration of his or her sins is not truly sincere and repentant. How does the apostle know this without hearing what the sins are? Again, say the person is truly repentant. How can the apostle, a human being who gains knowledge through his senses, forgive that person without knowing what exactly the forgiveness is being applied to?

The fact of having to confess your sins is so self-evident and implied. Jesus did not, and does not, stand on His dignity. He instituted. He does not explain the concessions of what He instituted. What He instituted unfolds and explains itself.