When I got married I was, like, "There's nothing to worry about because I know I'm not a terrible person and I'm pretty sure she's not a terrible person; I mean, just look at how HOT she is! God wouldn't let a terrible person be hot--it wouldn't be fair!" And my marriage has turned out all right (so far). But when I hear that other people are going to get married, I am overcome with anxiety on their behalf. Because, really, no matter how sterling your vetting process, it's pretty easy to slip through. Just look at all the wack-jobs you know who are (or have been) married. Most people's due diligence consists of "s/he looks great in those jeans I like, and s/he professes affinity for the same bits of popular culture I happen to like."
I was reminded of this when reading Wodehouse's Uneasy Money today. One character's subconscious is attempting to convince the man that he was lucky to have been released from his engagement.
Why on earth do you think that you would have been happy with this girl? What do you know about her except that she is a beauty? I grant you she's that, but are you aware of the infinitesimal part looks play in married life? My dear chap, better is it for a man that he marry a sympathetic gargoyle than a Venus with a streak of hardness in her. (p. 208)
I knew my wife for 17 years before we got married, and I STILL regularly think, "Man, I got lucky that she turned out to be okay." I guess we should all be grateful that so many people subscribe to the sunk cost fallacy.