Grant and I have been married for over 6 1/2 years and our philosophy on how marriage succeeds and survives has remained staunch. (like Winston Churchill- unrelated to this conversation but I have never been able to use the word "staunch" without having an image of the sober man pop into my head)
It really comes down to two things. Do you have the same faith and do you love hanging out together.
Regardless of how you define the word, the idea of faith is a spiritual reality that governs an individuals entire life. Faith determines a persons worldview, direction for their life- basically governs every decision a person makes every second of every minute of every hour of every day. If two people don't have the same faith, daily decisions will constantly be at odds. And over time, the little separations become two different roads leading you to different places. Even though Grant and I came from different backgrounds and attended radically different churches when we met- we had the same faith and even before we married each other we formed a "shining barrier". This is the hanging out together part.
This idea comes a book my older brother Daniel gave me called A Severe Mercy, which is one of the most incredible stories about the exclusivity of relationships I have ever read. The Shining Barrier is a series of cords a couple builds around themselves through daily decisions to make one another their only love. The first and obvious is to exclude all other romantic loves and only the two exist for each other. When Grant and I met we had actually very few things in common- we both loved music, smoking, hiking and camping, and road trips. We also liked making out and were horribly attracted to each other. Other then that- he spent his evenings eating take out and drinking beer, was fresh off the Ivy League school boat, drove an SUV for his camping gear, made fun of hippies and yuppies and was staunchly (Winston again) Presbyterian. I was an Anthropology major at the University of Colorado, long term vegetarian and organic foodie, hadn't shaved my legs in 3 years and read exclusively SARK and Brennan Manning for my theology texts. We were all wrong for each other.
But we had the same basic faith and we loved hanging out together. We were so attracted to each other that he pretended to enjoy going to Red Rocks with me to take pictures of flowers, and I ate crappy pub food just so we could be together. By the time we realized that our differences were going to make a relationship very complicated we had already created a thousand cords around ourselves and formed a Shining Barrier. We couldn't imagine it being this good with anyone else.
So that is how we think of marriage. It really isn't so complicated. We decide every day to stay together and make our relationship better. And the days we don't feel like it we keep the promises we made anyway. Because there is nothing like hearing that person walk through the door and realize how much you have been wanting them to come home.