We like it when decisions are clear, when there is right and wrong, when there is no gray. Unfortunately, that is not our world! So often, though, we get wound up over our own opinions, and we defend personal preferences as if they were the very heart of God's mercy.
Paul deals directly with two different disagreements in Rome, and he tells all sides to get along. Meat eaters be kind to vegetarians (who don't eat meat so as to avoid food sacrificed to idols), he says. Saturday worshipers have to respect Sunday worshipers. If death and life are no longer a worry to Christians, surely these small matters should not be!
The best way to avoid such quarreling is the law of opposites. Whatever opinion you hold, regardless of how convinced you are in your own heart of its correctness (Romans 14.5), do the opposite one in a while. Do you only worship with an organ leading music? Get yourself to a church with a praise band once a year. Does your preacher always use notes? Ask her not to from time to time. Do you always wear a suit to church? Wear shorts next week.
By purposefully doing the opposite of our comfort zone from time to time, we remind ourselves that we are dealing with opinions and preferences, not with the core of the Gospel. Just please don't make me sing "Borning Cry." It's a really awful hymn, and I don't like it...