This is another repost.
As believers we are to "Let the peace of Christ rule in our hearts," (Colossians 3:15). So often we see this verse either ignored or misapplied, and it is because of a misunderstanding or a false assumption of what this peace is. So let's see if we can garner a better, a correct understanding of what the peace of Christ is and how it is manifested in our lives.
First off, this verse is in the middle of a section where Paul is talking about our common ground in Christ because He is all and is in all (3:11), and how this is manifested in our life in the church in how we treat and respond to one another in the body. So its primary application is for believers in the context of church life. So this peace of Christ is to rule, act as arbiter or umpire, in our dealings and interactions with other believers, especially those in our local body.
Secondly, what is this peace that Christ has, that is to be the umpire of our hearts, and how did we come to possess it? In John 14:27 Christ says, "Peace I leave with you, My peace I give to you; not as the world gives do I give to you." So we see that it is Christ, Himself, that has given us His peace, and we have this peace because He has come and taken up residence in our heart; and we have become partakers of the divine nature (II Peter 1:4). The peace of Christ is the peace between Him and the Father. There was no enmity between the Father and the Son because Jesus always did the things that were pleasing to the Father (John 4:34, 5:30, 8:28-29, 8:42, 12:49, 14:10, 17:4, Matthew 3:17). Because of His perfect obedience to the Father there was unity and harmony between them with peace being the by-product of that unity and harmony. Christ had the same unity and harmony with the Father in His life here upon the earth that He had with the Father in eternity past. This is why Jesus could say, "I and the Father are One." (John 10:30, 17:11, 22-23). The body of Christ is to have and manifest the same unity and harmony within itself that exists between Christ and the Father (John 17:20-23).
Before salvation we were at enmity with God, we were His very enemies (Romans 5:10), but God reconciled us to Himself through His Son (Romans 5:10, II Corinthians 5:18-19). The Father and the Son were at perfect peace, so that, "Therefore, having been justified by faith, we have peace with God through our Lord Jesus Christ." (Romans 5:29). So when we let the peace of Christ rule in our hearts it means that we are not to do anything that would disrupt our peace with our heavenly Father. Our peace with Him should guide our decision making and govern our responses. Within the context of this section of Colossians we see this worked out in our compassion, gentleness, kindness, humility, patience, forbearance, forgiveness, and love within the body of Christ. We have peace with God and one another as we practice these Christian graces mentioned here; and it should then be a part of our life so that, "As far as it depends on you, be at peace with all men." (Romans 12:18).
However, this peace, the peace of Christ, is not a peace at the expense of righteousness, or peace at the expense of the truth. It does not compromise righteousness or truth, but instead it is a peace at the expense of the self, at the expense of personal "rights", at the expense of personal desires, at the expense of personal comfort. It is a peace at the expense of personal ambitions, personal glory, at the expense of personal achievements, or personal recognition. It is peace because we have given up ourselves, and is part of taking up our cross daily and following after (living in like manner) Him, who gave Himself up.
So, first, be sure that you are at peace with God through faith in His Son, the Lord Jesus Christ. Then pray a prayer of thanksgiving to God for establishing peace with you, His enemy, and reconciling you to Himself through the blood of the cross. Now live a life of peace with God through how you live your life with others in the body, and in the world; but not at the expense of righteousness or the truth.