Marriage isn't the end-point of a relationship. It's just a stepping stone, one aspect of a long-term evolution between two people who have, for whatever reason, decided to take a leap of faith and say, 'Well, hey, this is a person who I want to try with for the rest of my life.' Which is not a guarantee of perfection - far from it.
They were married before they were friends, which is another way of saying:Their marriage was the occasion of their friendship.They were married before they noticed many small differences in background, aspiration, education, ambition. (...)Noting such differences, Leah was in some sense disappointed in herself that they did not cause real conflict between them. It was hard to get used to the fact that the pleasure her body found in his, and vice versa, should so easily overrule the many objections she had, or should have had, or thought she should have had.