I don't recall the Word stating that we need to confess our "sins" to one another. It does say in James 5 that we need to confess our "trespasses" to one another, however. Trespasses and sins are two different things, IMO. When the Word is talking about trespasses I think it is in regard to us trespassing against other people. So, when you trespass against another person you need to confess it to them. Not all sin, however, is a trespass against another person.
"What you do does not define who you are; it's who you are that defines what you do."
-- Dr. Neil T. Anderson