In the Bible, peace begins with God — being at peace with him through faith — and reaches the heart and our relationships. Jesus did not promise a world without trouble; he promised his peace in the middle of it.
These things I have spoken unto you, that in me ye might have peace. In the world ye shall have tribulation: but be of good cheer; I have overcome the world.
Jesus is realistic: in the world there will be trouble. Peace is found in him, who has already overcome.
The LORD bless thee, and keep thee: The LORD make his face shine upon thee, and be gracious unto thee: The LORD lift up his countenance upon thee, and give thee peace.
The priestly blessing ends with peace — it is what God wants to place upon his people.