We understand that from a worldly point of view peace is mainly the absence of hostilities. Whether people love each other is not and cannot be a concern for governments trying to establish order. But in Christ's kingdom things are a little different. Christ isn't so much concerned with outward morality as he is inward godliness. One big reason is that from a good heart comes good deeds. This is why Jesus tells us that it is wrong for his people not only to murder but to even to want to murder someone. Because simply not killing someone is not a complete reflection on the holiness of God but loving your neighbor and so not trespassing against him is.
So for a Christian, having peace with God will bring an inner peace that will allow us to have peace with those around us. By this we do not mean that we will force ourselves to not mistreat others but instead we will have a genuine love and concern for others. This isn't automatic but comes as we "abide" in Christ. Jesus told us that fruit is only produced by abiding in him. I believe this is done not by "letting go and letting the Spirit 'control' us" in some mystical way but by abiding in his word.
Abiding in God's Word isn't just a matter of having daily devotions and reading a few passages or even a lot of passages. It means meditating on what you have read. Thinking about what it means in its context and how this information should affect the way you think. None of this can be done properly without the power of the Holy Spirit but it equally can't be done without ingesting the Word that He has been given as a guide. We speak sometimes of life application and that is okay but we first need some heart application.
Let's take the subject of peace for instance. What is wrong if we can't get along with others or have a problem with anger and strife? What is wrong when we never seem to get victory over our "nerves" and are constantly overcome with worry? It is one thing to believe in Jesus for the forgiveness of sins and to have peace with God. But it is another thing to abide in these truths, to meditate on them and think through them and work them out and then apply them in our lives so that such truths actually rule the way we live.
We read in Col 3:15-16 And let the peace of Christ rule in your hearts, to which indeed you were called in one body. And be thankful. Let the word of Christ dwell in you richly, teaching and admonishing one another in all wisdom, singing psalms and hymns and spiritual songs, with thankfulness in your hearts to God. How does the fact that you have peace with God translate into a peace that rules the way you live? Perhaps the next verse offers some light. Let the Word of God be what drives the way you think. It seems this is one of the points Paul is making.
If you are so full of yourself that you can't get along with others or be content with God's providential care then you aren't keeping the truth of God's Word in the forefront of your mind. You have been reconciled to God and he is taking care of you and has promised to bring you unto himself and let you gaze at his glory for eternity. None of these things you deserve and Hell was your future until he graciously came to you in Christ. If this doesn't bring a peace in your heart and mind, what will?
Have we been faithful to attend the preaching and faithful in daily devotions but still failing to abide in Christ by letting his Word permeate our life?