There will be times when we have to take a stand on our convictions no matter the fuss and hard feelings it may cause between some that do not hold to our beliefs. We are not called to agree with the unbeliever that there is no God, just for the sake of keeping things "pleasant" between us. But always, we are to stand firm even in those areas that we differ, with love and a peaceful purpose, rather than to push our own desires.
Are the things we differ about of eternal consequence? Or are we simply wanting things the way we think is more pleasing? Proverbs 17:1 says, "Better is a dry morsel with quiet than a house full of feasting with strife." People who constantly point out the faults and differences in others are draining. But on the other hand, those who choose to overlook matters of small importance, and encourage and care about others, can do so much good just by their example of thinking of others first!
If the issue is truly a biblical matter, than we can trust the Lord to work in the heart of the other. That doesn't mean we won't be a part of the way he breaks them. Following Christ's leading often times takes us to a point where we have to encourage each other in good doing- or maybe even outright rebuking wrong doing. But if we are truly concerned about the well-being of a soul, than we will be able to deal peaceably with others. They may not take it peaceably, but if they show anger at your concern, Christ says in Matthew 5:39, "But I say to you, Do not resist the one who is evil. But if anyone slaps you on the right cheek, turn to him the other also."
If the matter does not hold eternal weight, than, in the words of Philippians 2, "Do nothing from selfish ambition or conceit, but in humility count others more significant than yourselves." This is hard. Our flesh wants what we want. And it may be something "good". But that does not mean that it is better than all other opinions. It just means that, as individual people, we have individual ideas. And the Lord has made us that way to give us a wider array of gifts- to use for furthering His kingdom :)!