This was a question recently posed on a forum I sometimes visit, and I got to thinking about why it was I actually married Ed. This was my response:
This may sound silly and simplistic at first, and it is, but hear me out.
I married my husband because I like him and wanted to create a life with him. I make a conscious effort to continue finding things about my husband that I like. He does things that frustrate me too - as I'm sure there are things I do that bug him - but I try very hard to ignore or conveniently forget those things and focus on the things I like about him.
I loved him very soon after we met and the feeling was mutual, and inexplicably, even before we met (we're an Internet romance), we knew that this was The Person (tm). We discussed our thoughts about our futures with each other before we were even dating, just getting a feel about each other. We were open with each other; I have found him easier to be open with than anyone I've ever met; I can share with him my vulnerabilities and fears, and he knows the best ways to comfort and support me.
We have similar senses of humor; we enjoy talking to each other about our days at work. We like travel to weird places and thinking about where we'd like to travel (this is big; my husband is former commercial pilot and at one point he'd been involved with a woman who was afraid to fly and panicked whenever he went to work, whereas I've held a passport since I was 7 - 30 years ago, now - and lived abroad, and dig airplanes and airports).
We travel together well. More than anything else, this for us predicated success. I've heard Slate's Prudence emphasize the importance of sleeping together before marriage ("because otherwise how else will you know you're compatible?") but that we took a two-week multi-European-country trip before we got married (although after we'd gotten engaged; we had planned the trip before we got engaged) spoke volumes of how well we could navigate new landscapes and handle potentially difficult experiences on the fly. I'd actually say that traveling in such a capacity beforehand is a good predicator for success, but that's just my experience; your mileage may vary.
My husband supports my career goals, and doesn't think being a teacher is ridiculous or that my income is inconsequential. He thinks I should teach because I love it and it makes me happy. Period.