@tango, Sin goes much deeper than actions. It involves selfish attitudes, desires, thoughts, as well as feelings. We don't need to confess to others unless the sin directly involves them. God as our Judge has already taken away his "guilty" verdict from us as true believers (justification), but our sins still remain lurking in our sinful natures.
We have to ask God what inner sins still remain within us, for they are still there. As a result, we need to ask that God will cleanse our lives of those sins daily through Jesus' death, as Jesus taught us in the Lord's Prayer, "And forgive us our debts, as we also have forgiven our debtors" (Matthew 6:12). Read all of the letters or epistles, especially the second parts of them (for example, Colossians 3-4, Ephesians 4-6, Galatians 5-6, Romans 12-16, and Hebrews 12-16), to discover the commands about sins that we don't often think about.