That may sound like an unusual heading. You should be concerned about sin inasmuch as you should diligently seek to avoid it. But if you were to realize that your understanding of the Mercy of God is but a drop of water compared to the ocean, you would not allow your concerns to turn into worries. To be concerned is to be conscientious and being conscientious is a grace. But when you look at your sin, honestly and thoroughly, in the light of the Mercy of God, you will never worry that your sin is too much for God. His greatest desire is to wipe it away in an instant, forever (See Diary #1665).
Reflect upon whether you are comfortable facing your sins with exceptional honesty. If you are not then that is a sign that you do not understand His infinite Mercy. Know that comprehending His Mercy is the best cure for every sin.
Lord, I see my sin but I want to see it more clearly. Give me the grace of knowing Your perfect Mercy so that I can face my sin without worry and without fear. Jesus, I trust in You.