The Peace of God is to Rule the Heart of a Christian
And let the peace of God rule in your hearts, to which also you were called in one body; and be thankful.
Let the word of Christ dwell in you richly in all wisdom, teaching and admonishing one another in psalms and hymns and spiritual songs, singing with grace in your hearts to the Lord.
And whatever you do in word or deed, do all in the name of the Lord Jesus, giving thanks to God the Father through Him.
Here 'rule' literally means 'sit as umpire'. The false teacher, as a self-constituted umpire, defrauds you of your prize; but if the peace of Christ be your umpire ruling in your hearts, your reward is sure.
'Let the peace of Christ act as umpire when anger, envy, and such passions arise; and restrain them.' Let not those passions give the award, so that you should be swayed by them, but let Christ’s peace be the decider of everything. (Reference: Jamieson-Fauset-Brown)