Values must align........
And a lot more. Opposites may attract sexually, but they don't last. (The nice girl who likes, "bad boys", or the computer salesman who likes pole dancers and biker babes). There are certain things that you both have to line up on the same side together. Or else there is eventually going to be trouble..... Lot's of it. Until you both get fed up, and go your separate ways.
3 good examples... Politics, religion, finance, If one's a spender and the other a saver, look out. Even lifestyle. If you like guns and she hates them, look out. Another thing is this total nonsense of, "going out with the girls". Or having, "girls night out".
Every guy I've known over the years that has allowed this in his marriage, ended up divorced. Every single one of them. You might as well just let her date. Think of it this way. Look at all the male friends and coworkers you hang around with, and like the most.
The woman has to be, or at least become your best buddy in the same regard. Otherwise both of you are going to constantly have to be "giving in" to each other. Over time that is going to have a major effect on your, (and her), overall happiness.
If you are from different ends of the political and religious spectrum, it will more than likely be a disaster. Just look at this forum as an example. We can't agree on the length of OCI's.
Now try to imagine if we allowed religious and political forums here. It would descend into a bloodbath within 10 posts. Which is why they won't allow either here. As do other forums.
A marriage is no different. If you both don't see eye to eye on politics and religion, your tongues will eventually swell up and choke the both of you, from constantly having to bite them.
Naturally all of the above is very difficult to achieve between 2 people who are constantly living under the same roof. Not to mention sleeping in the same bed.
Which is why the current divorce rate is right around 50% after 7 years. And why marriage between 20 and 30 years olds is down 60% overall since the 70's. As was once said, "I can accept marriage as an institution. I'm just not ready for an institution".