You have set our iniquities before you,The words "have set" could be translated as "placed" or "positioned". It is active. The word "before" conveys the idea of a conspicuousness. It is directly in the face. So, in other words, God has actively set our sins directly before his face, even our secret sins.
our secret sins in the light of your presence.
I believe that the key is found at the end of this verse. It is just a hint, but the fact that these sins are in the light of God's presence is very important. Bringing our lives under the light is ultimately an act of love, it is not a way of God saying, "Look what you did!"
Walk away from this verse with this: First, you need to know in your heart that there are no sins that are secret from God. Secondly, He brings these sins into the light for your own good.