Sin is a step away from God's presence.
It's like when you smoke. You know you did something so you couldn't go near your Dad and Mom. No matter how you mask it, it's knowing that you smoked that creates the greatest stench.
But praise God, because by the blood of Jesus, not only have I been scrubbed clean of any stench, but I have also been set free of any obligation to smoke - or sin, for that matter. I give the Lord all the glory for this revelation.