You may not always be on the same page, but it helps to be reading the same book.
An unequally yoked marriage, one in which one spouse is Christian and the other a non-believer, is discouraged in the Bible. Most Christians believe it's important to be equally yoked in marriage — meaning both spouses share the same faith, and quite frankly — I agree. Not because I'm a firm believer in biblical marriage and following scripture passages to a T, but if you're going to decide to spend your life with someone, it's probably a good idea to be on the same page about what's possibly the biggest and most important aspect of your life.
(FYI: The passage from 2 Corinthians that refers to not being yoked with unbelievers doesn't actually say anything about marriage, so if you want to get really biblical you'll have to ditch all your non-believing friends/acquaintances/relatives.)
For many, religion is more than just a part of their life; it's something that cannot be compartmentalized for the sake of a relationship.
Religion helps shape our lives in all areas: how we spend our time, how we spend our money, how we raise our children, how we choose our job. These are the sorts of things that can spell disaster for your relationship, and compromise isn't easy when you're looking at these issues from a religious standpoint.
Your faith (or lack thereof) determines so much about the way you view the world and move through your life. When your faith is at the core of your being, you crave someone who will understand you on a spiritual level and help you grow in your faith.
If you're an atheist, you want someone who can appreciate the world alongside you without the trappings of religious doctrine. Personally, I want someone who understands me at the core of my being and I don't want to search outside of my marriage to find someone who fulfills that need.
My equally yoked marriage has made my life so much easier. My husband and I often have the same sentiments about how we want to raise our kids and spend our free time because our goals are the same — to raise our kids to become morally conscious and kind adults. We agree on where we should spend and donate our shared money. We share the life-changing articles we read, the shows we watch, the podcasts we love — to help each other and our relationship grow.
When you don't get to share the experiences that are so vital to your personal growth, it's easy to feel like you and your spouse are growing apart. I know women who go to church without their husbands, pray for them regularly, and work hard on their marriage but they always feel there is a gap which they can't bridge alone.
In marriage, you need someone who will honor who you are and help you become the kind of person you aspire to be. You may not always be on the same page, but it helps to be reading the same book. Your core values should bind you together, not separate you further. And for many, faith or non-belief is what informs those core values.
If there's such a divide that you cannot empathize with your partner's belief system, a huge part of your life is disconnected from your spouse.
I'm not saying it's impossible. Empathy can and will bridge seemingly impossible gaps. I know many people who live in mixed-faith marriages that are fulfilling and successful but they aren't without hardship or the secret hope that one person will "convert."
Love can only get you so far when God is in the picture. When you're looking at the rest of your life with one person, love isn't always enough.