Peace is completeness, soundness, and well-being of a whole person. Christians are to be at peace with others, which happens to be healthy for a person's body. [Consider Rewording] Christians are to live at peace not with just anyone they want, but with everyone to the best of their ability and whenever possible.
A Christian can find peace from loving God's law. It is a fruit of righteousness  and of the Spirit, so it is evidence of righteousness and Holy Spirit in their lives. The peace that comes from God is beyond anyone's understanding. Christians also get peace from discipline, for it produces a harvest of peace and righteousness for those trained by discipline. Righteousness and peace are found together here because of peace being a fruit of righteousness, as mentioned above.
Christians are to seek peace and pursue it  through righteousness. Those who seek peace find peace when they love God's law. Holy Spirit gives peace to those who want (and even need) peace in a way that cannot be understood. Like a loving Father, God has Christians' best interests in mind when He commanded them to live in peace; recall that it gives life to the body. Jesus said that those who seek will find  so Christians should seek and pursue peace.