Having both lived with people and married one, and being absolutely atheistic, and someone who previously thought "it's just a piece of paper"... it's not, and I was wrong. Being married is different.

There's also some reasons to believe that cohabitating before marriage (to the same person) leads to higher rates of divorce: http://www.nytimes.com/2012/04/15/opinion/sunday/the-downsid...

What's different about it? I'm not 100% sure. But none of the guys I lived with (for years) caused me the kind of angst that my husband did at first, when I moved in with him and immediately got married a few weeks after. (Prior, we didn't really live together before marriage except for weeks/months at a time at the others' apartment, living in different countries.) I'd never had a terrible "adjustment period" before, but did this time… and believe me, on paper, previous boyfriends were way more annoying than my husband was, even in those first few months. We got through it, obviously. I'm grateful for him every day.

I'd always been a committed and faithful girlfriend to the others but it just isn't the same as being married. Which surprised me as much as anyone.

Intellectual types underrate the importance of ceremony. I now believe that's a mistake.