"The truth is that the more intimately you know someone, the more clearly you'll see their flaws. That's just the way it is. This is why marriages fail, why children are abandoned, why friendships don't last. You might think you love someone until you see the way they act when they're out of money or under pressure or hungry, for goodness' sake. Love is something different. Love is choosing to serve someone and be with someone in spite of their filthy heart. Love is patient and kind, love is deliberate. Love is hard. Love is pain and sacrifice, it's seeing the darkness in another person and defying the impulse to jump ship."
Two other things I've heard about marriages that seem to last forever...
When an old man wouldn't leave his wife's side while she lay in the hospital was asked "How have you two remained married for so many years?" He replied "Just stay in the room. Whatever they throw at you, whatever they say, whatever they do, just stay in the room. In the room is where the relationship happens."
The other is "We never wanted to get divorced at the same time."