Marriage is the reunion of the separated duad.Originally you were one.You are now two in the world,but the recognition of the spiritual identity is what marriage is.
Its different from a love affair.
It has nothing to do with that.Its another Psychological plane of experience.When people get married because thay think its a long-time affairs,they will be divorced very soon, because all love affairs end is disappointment.
But marriage is recognition of a spiritual identity .
If marriage is not a first priority in your life,you are not married.

The marriage means the two that are one,the two become one flesh.

If the marriage lasts long enough,and if you are acquiescing constantly to it instead of to individual personal whim,you come to realize that that is true -the two really are one.

Marriage is a relationship. When you make the sacrifice in marriage, you’re sacrificing not to each other but to unity in a relationship. The Chinese image of the Tao, with the dark and light interacting-that’s the relationship of yang and yin, male and female, which is what a marriage is. And that’s what you have become when you have married. You’re no longer this one alone; your identity is in a relationship. Marriage is not a simple love affair, it’s an ordeal, and the ordeal is the sacrifice of ego to a relationship in which two have become one.

“A love affair has to do with immediate personal satisfaction. But marriage is an ordeal; it means yielding, time and again. That’s why it’s a sacrament: you give up your personal simplicity to participate in a relationship. And when you’re giving, you’re not giving to the other person: you’re giving to the relationship. And if you realize you are in the relationship just as the other person is, then it becomes life building, a life fostering and enriching experience, not an impoverishment because you’re giving to somebody else … This is the challenge of a marriage.”