Notice carefully what Paul names as the reason for making unity and peace: the value we place on our calling. If, in our heart of hearts, we consider it of small value, our conduct, especially toward our brethren, will reveal it and work to produce contention and disunity. Thus John writes, "If someone says, 'I love God,' and hates his brother he is a liar; for he who does not love his brother whom he has seen, how can he love God whom he has not seen?" (I John 4:20).
Paul next counsels us to choose to conduct ourselves humbly. Humility is pride's opposite. If pride only produces contention, it follows that humility will work to soothe, calm, heal, and unify. He advises us to cultivate meekness or gentleness, the opposite of the self-assertiveness that our contemporary culture promotes so strongly. Self-assertiveness is competitive determination to press one's will at all costs. This approach may indeed "win" battles over other brethren, but it might be helpful to remember God's counsel in Proverbs 15:1, "A soft answer turns away wrath, but a harsh word stirs up anger." James declares that godly wisdom is "gentle, willing to yield, full of mercy" (James 3:17).
Then Paul counsels that we be patient; likewise, James counsels us to "let patience have its perfect work" (James 1:4). We often want quick resolutions to the irritations between us, which is certainly understandable since we want to get rid of the burden those differences impose. But we must understand that speedy solutions are not always possible. Interestingly, in Paul's letter to the Philippians, he does not use his apostolic authority to drive the two feuding women into a forced solution (Philippians 4:1). Some problems are deeply buried within both sides of the contention, so finally Paul admonishes us to forbear with each other in love. Essentially, he says to "put up with it" or endure it, doing nothing to bring the other party down in the eyes of others and vainly elevate the self. This is peacemaking through living by godly character.
Yet another aspect to the Christian duty of peacemaking is our privilege by prayer to invoke God's mercy upon the world, the church, and individuals we know are having difficulties or whom we perceive God may be punishing. This is one of the sacrifices of righteousness mentioned in relation to Psalm 4:5. The Bible provides many examples of godly people doing this. Abraham prayed for Sodom, Gomorrah, and probably Lot too, when the division between them and God was so great that He had to destroy the cities (Genesis 18:16-33). Moses interceded for Israel before God following the Golden Calf incident (Exodus 33:11-14). Aaron ran through the camp of Israel with a smoking censer (a symbol of the prayers of the saints) following another of Israel's rebellions that greatly disturbed the peace between them and God (Numbers 16:44-50). In each case, God relented to some degree. We will probably never know in this life how much our prayers affect the course of division or how much others—even the wicked—gained as a result of our intercession, but we should find comfort knowing that we have done at least this much toward making peace.