The beginning of our peace with God is when we realize that we have been reconciled to God through His Son Jesus (2 Cor 5:19).  In justification by faith we have peace with God (Rom 5:1).  Then the peace of God guards our inner persons as well as our thoughts.  It presides over us in unexplainable and incomprehensible ways, even in the midst of the greatest trials of our lives.  We know we have the peace of God and go forward to live our lives, even when all around us seems to be falling apart.

“And the peace of God, which surpasses all comprehension, will guard your hearts and your minds in Christ Jesus.” Phil 4:7 (NASB)