Addendum

Then your sister-in-law posts this on Facebook and you think, thank you Universe, this makes much more sense (than the book I finished this morning).  And, see what I would have missed if I curtailed my time online?  :-p

Some choice excerpts (the author's name is Susan Piver):

Marriage is a commitment to share love, have sex and try to stay together with this one person, right? Well maybe, but I couldn't promise to do these things. I knew I couldn't say, "I do" to love--feelings change, and keep changing. I also knew I couldn't say yes to wanting to have sex with him for the rest of my life--desire is unpredictable. And ask him to commit to me? Which me? I couldn't commit to remaining the same me. So if you can't say yes to love, sex, or remaining the one each fell in love with, what are you agreeing to when you commit to a relationship?

I said yes to the unfolding, impenetrable arc of uncertainty. I guess I thought that finding love was an endpoint, that some kind of search was over and I would find home. We would leap over the threshold together into whatever we imagined our ideal cottage to be. But really we stepped through a crazy looking glass. No matter how hard we tried, how madly in love we were, or how skillfully we planned our life together, there was complete uncertainty about what the connection would feel like from day to day. I could give all the love I had (with great joy) and get back a blank stare. I could wake up as my crankiest, most sullen and narcissistic self, roll over, and greet the face of unconditional acceptance. Or not. It's like the weather: you can try to read the signs and guess about atmospheric conditions, but really there's no telling.
 
As far as I can see, the relationship never stabilizes, ever. In which case you can't actually promise each other anything. This is how it works. I have no idea why.

I wish I had known that when you live with someone for a long time, there is continuous, mind-blowing irritation. (Okay, I did know this, but I forgot.) Often the irritation arises when you try to replace your actual partner with who you wish he or she was, because they always figure out a way to tell you how unlike your projection they really are. Once you pick yourself up, that gives you yet another opportunity to choose between who this person is and who you sort of hoped he or she was. No matter how many times I prompt my husband with the correct lines for his role, he does not get into character. This irritates me. We have to throw away the script and just begin to improvise. You're playing you and I'm playing me. Go.

I didn't really understand that love does not arise, abide, or dissolve in connection with any particular feeling. It has almost nothing to do with feeling. (Nor does it seem to be a gesture, a commitment to stay, becoming best friends, or anything else I might have thought.) Love has become a container in which we live. Through time, riding mysterious waves of passion, aggression, and ignorance (and boredom), I think we began to live within love itself. At least I did. Each time I have opened up, extended myself, accepted what was being offered to me, stepped beyond my comfort zone to embrace him, the structure has been reinforced. I no longer have any idea if I love my husband or not. I can't imagine what the feelings I have for him could be called. I've even given up trying to love him. Our relationship is what gives us love, not the other way around. This is how it is.
 
And here's something else I've learned about a relationship: Okay, so it's not what you think it's going to be, the feelings are always changing, and you're going to have to say goodbye someday. But when you find your true love, there is something inside that simply and inexplicably says hello to him. Yes to him. Of course to him. Certainly. Obviously it's you. There is no choice. I do.