This is the trinity of blessing. Grace is God giving us what we do not deserve. Mercy is God not giving us what we do deserve. And peace is the result of receiving what we do not deserve and not receiving what we do deserve. We know peace through the grace of God.
Grace always precedes peace.
The denial of grace is legalism. Anytime the devil sees a person celebrating grace, he will move in to break up the joy and happiness. A legalist had come in to the city of Crete and had begun to preach strict legalism. The legalism subverts whole houses, and splits churches. The devil cannot handle the grace of God.