How Do We Get From Here to There?

It's always sad to hear of friends' marriage melt-downs. It should be beyond the power to shock; this is a modern world but it is, nonetheless shocking. They seemed so normal, so loving to each other, so attuned to each other's lives, supportive of each other's careers....etc. etc.
I'm old enough to remember Ann Landers' breakup. Jules had left her a note at the breakfast table. Basically it said: Dear Ann, found someone, gotta go. The guru of failing marriages had, herself, failed.
We start out so optimistic; so naïve and happy.

This is not the place to get all statistic-y; we all know them. But how is it that some of us are married forEVER? What is it about our relationships that is different? I know that we are not better, kinder, saintlier. If we're not, why do we deserve to be luckier?
My sister and I have long discussions; on one thing we are agreed. 'Love' is a ridiculously overworked, misused and misunderstood word. 'Loving someone to bits' is not the same thing as having 'love'. Being in love is an emotional state. Loving someone is an attitude. Love is a working term; it means all the things the Biblical verse says and that is not easy. However, as much as I have to suck up all my true-loves flaws, so does he suck mine up.
There are days when I am so weary of compromise that I think we're all whores....trading this for that. Is it worth it? Then there are the exciting moments when I glimpse this man from a new angle and my breath catches  in my throat and my legs go wobbly. The fact that we don't give up compromising is 'love', the other is 'in love'.
Do we give up on our marriages because we expect too much? Do we expect to be euphoric all the time? Is it misleading advertising?
Should a new spouse go about in fear of her/his marriage? When is it safe to bask in some security? Are we idiots to feel safe?
Luck, luck, luck. And stubbornness. Maybe.