All my life, I've gone to church. And all my life, I've heard the Christian's around me sing about peace. Perfect peace, no less. Yet many of these same Christian's have never experienced it and don't think they can.
There are at least three different meanings of the word peace in scripture, each contrasted sharply by three non-Christian experiences in the life of believers.
Peace with God. This has nothing to do with us, and everything to do with God. This is the peace that God decided to declare was true between us and Him through the work of Christ. He did it as a gift, not because of anything we have done or could do. It's the centerpiece of the gospel message that they say they accepted, yet many Christian's worry that God isn't pleased with them.
Peace of mind. This one comes to the Christian who believes in the previous one. Christian's are told to "be anxious for nothing" and experience a "peace that passes understanding," yet many Christian's have a life of anxiety that is as intense as anyone else in the world.
Peace with others. This is far and away the kind that scripture talks about the most, particularly between fellow believers. This is intended to be the most defining of characteristics present in believers, serving as proof to the world that Christ is from God, yet many Christians nurse grudges, excusing them, protecting them, ignoring the promptings of the Spirit at work within them.
Near the top of the Spirit-filled Christian's priority list lies these words of Paul: "As far as it depends on you, live at peace with everyone." - Romans 12:18