Religion against a relationship to work?

Do you think religion matters most for a certain relationship to work and last for a long time?why or why not. Well, leave that question in your mind. But on my own thoughts, it really does. Well, it's actually hard to live with someone that has a different religion. Especially if it would contradict with your traditions and belief. Even you say that you would respect each other's religion, time will come that there would really be a conflict. So what can you say?