When we confess with our mouths that Christ is the Lord, and believe it in our hearts, it's the greatest confession we can ever make. We acknowledge Him as our Savior. But we also confess our trespasses before the Lord when we sin. To confess our sins is to agree with God that we have sinned and then we must repent and turn away from them. We also confess our faith in Christ by never denying Him in public.
"Whoever acknowledges Me before others, I will also acknowledge before My Father in heaven."- Matthew 10:32