(I am not addressing the marriage issue, as I have never been married. The following is more of general advice when dealing with theists as a whole).
I can definitely relate in regards to wondering why people still desperately cling to what I consider to be an outdated belief system based around a mythology that had been cobbled together from previous (and equally fictitious) religions.
In my late teens/early twenties, this opinion manifested itself in anger and scorn towards Christians (and theists in general) whom I felt were just scientifically illiterate individuals. It was extremely difficult at the time not to openly mock those believers I would sometimes find myself engaged in conversation with.
The one, huge problem with an attitude such as this... and it took me until my mid-to-late thirties to figure this out... is that it is counterproductive to trying to understand why Christians believe what they do, never mind actually attempting to try and explain to them how their God-tinted worldview does not match up with what we now know about reality.
My advice to you is to try and be patient and sympathetic with those believers around you. Remember, most of them were probably indoctrinated in to their religion at an early age and were surrounded by others of a similar faith growing up. Also, keep in mind that the belief in an afterlife where everyone you have ever known and loved (as long as they lived a "good" life) will eventually be reunited is a very comforting thought for them in such an oftentimes hellish world we see on the evening news every night.
Now, I am not suggesting that you do not challenge their beliefs if the subject comes up. It's all about the tone you take when trying to educate them, for example, with how there is no historical or geological evidence of a "world-wide" flood such as the one described in the Bible. Calmly show them the mountains of scientific evidence to back up your claims instead of reacting with "are you really that stupid?". Trust me, that approach never works.