If we confess our sins,
he is faithful and just
and will forgive us our sins
and purify us from all unrighteousness.
To confess our sins means to agree with God about our sins. To agree that we have once again missed the mark. But agreeing with God is walking in the light, therefore God, who is faithful and just no matter how we are, forgives and purifies us.
Are you in agreement with God about your sins? Or do you try to justify your actions?