I think that this is a good question...and as one in my third marriage, I think that I am in a most beautiful position to answer this question to the fullest extent. When I was in an illusioned state of being I thought that marriage was about this deep emotion that I was feeling for another person. This person who it seemed had entered my world and was everything to me and that it seemed that I could not live without. In my mind and heart we were perfect and meant to be.
Only time, after we were married of course would allow me to see that we were truly different in our thoughts, our perceptions, what we wanted out of life, our goals and our beliefs. By this time we already had children together and I had a choice...stay with her because of the children or move on and simply support them. I chose to move on and simply support them. I understood then that I would be a fool to sacrifice the reality of who I was "for the sake of the children". That in essence would have meant at least 18 years of turmoil, of contradictions and of my own life perpetrating a fraud for the sake of the children. Nah, that wasn't going to work. Sure, the sex was good but outside of that we were like night and day.
Only time and growth would allow me to see and understand what it was that took place and why I felt the way that I did about this woman. I learned over time that there is something called "the law of chemical affinity". This law is the law that says and proves that your exact opposite or better yet, attraction from a physical chemical level is out there. What this means is that there is someone out there who you are a perfect match for on a chemical, physical level. In other words the two of you are like magnets and metal. A direct attraction and you perfectly match each other and in bed are like a union that was meant to be...and come hell or high water the two of you will find a way to be together, whether you are married already or not.
I went through this twice in my life. The first time I dismissed it because I saw the shape of the woman and chalked it up as lust. The second time I didn't see anything as it relates to the woman. I couldn't even see her face and had simply passed her by in a snow storm...yet I felt my knees buckle as I passed her and my heart started beating off the meter. If you can find someone like this and you both have the same beliefs or goals in common, the sky is the limits in terms of what you will accomplish. In essence you are a union both in bed and out of it and the two of you don't care which one you are in....that my brothers and sisters is like the perfect marriage.
Outside of the reality that I just painted, marriage in general is like, " I'm willing to put up with your b.s. if you're willing to put up with mines...and in general that's what a lot of us have.