I'll start with my own brief answer. Lifelong marriage is the cornerstone of Christian sexual morality. It is also God's design for the family and the structure in which children should be conceived and raised. If you want to have sex and/or have children, lifelong marriage is the only biblically sanctioned way to go about this.
Love and happiness are benefits which very often come with following God's plan, and there are specific commandments to both men and women as to how they are to treat their spouse. I also have argued strongly that in our current legal and cultural climate it is wrong to marry someone you haven't been able to fall in love with. But making marriage about love and happiness inevitably turns it into something different, especially in a world where the law provides direct incentives to wives who manage to become unhaaaapy.
There are many passages about marriage in the Bible, but 1 Corinthians 7:1-16 is probably the key New Testament passage and it reveals a lot about God's perspective on marriage.
1 Corinthians 7:1-16
1 Now for the matters you wrote about: "It is good for a man not to have sexual relations with a woman." 2 But since sexual immorality is occurring, each man should have sexual relations with his own wife, and each woman with her own husband. 3 The husband should fulfill his marital duty to his wife, and likewise the wife to her husband. 4 The wife does not have authority over her own body but yields it to her husband. In the same way, the husband does not have authority over his own body but yields it to his wife. 5 Do not deprive each other except perhaps by mutual consent and for a time, so that you may devote yourselves to prayer. Then come together again so that Satan will not tempt you because of your lack of self-control. 6 I say this as a concession, not as a command. 7 I wish that all of you were as I am. But each of you has your own gift from God; one has this gift, another has that.
8 Now to the unmarried[a] and the widows I say: It is good for them to stay unmarried, as I do. 9 But if they cannot control themselves, they should marry, for it is better to marry than to burn with passion.
10 To the married I give this command (not I, but the Lord): A wife must not separate from her husband. 11 But if she does, she must remain unmarried or else be reconciled to her husband. And a husband must not divorce his wife.
12 To the rest I say this (I, not the Lord): If any brother has a wife who is not a believer and she is willing to live with him, he must not divorce her. 13 And if a woman has a husband who is not a believer and he is willing to live with her, she must not divorce him. 14 For the unbelieving husband has been sanctified through his wife, and the unbelieving wife has been sanctified through her believing husband. Otherwise your children would be unclean, but as it is, they are holy.
15 But if the unbeliever leaves, let it be so. The brother or the sister is not bound in such circumstances; God has called us to live in peace. 16 How do you know, wife, whether you will save your husband? Or, how do you know, husband, whether you will save your wife?
Verses 1, 7, 8-9: The best way to live is unmarried and abstinent, because this condition enables a person to focus wholly on serving God. However, God created the excellent institution of marriage for the majority of us who are not gifted in this way.
Verses 2-6, 9: Marriage is about sexual purity. God has given us two acceptable modes of sexuality: single and abstinent, or married and sexually active with your spouse only. "For it is better to marry than to burn with passion".
Verses 10-11: Christians are not to divorce. A Christian who leaves his or her spouse is expected to reconcile the marriage or else remain single and celibate. In Matthew 5:31-32 makes an allowance for divorce in the case of sexual immorality.
Verses 12-16: A Christian must not divorce an unbelieving spouse, but if the unbelieving spouse seeks a divorce then the Christian must let the spouse go. "Let it be so" is a command, and the only instance in the Bible where divorce is commanded. Furthermore, the believing spouse is free from all obligations to the unbelieving spouse. Why? "God has called us to live in peace." Matthew 18:15-17 should also be considered, as Jesus instructs that a person who claims to be a Christian and yet ultimately refuses to submit to church discipline should be treated as an unbeliever ("excommunicated" is a commonly used term).
So, no where is "happiness" mentioned. In Genesis 2 God says "It is not good for the man to be alone. I will make a helper suitable for him.", but in what ways is having a companion beneficial? From the 1 Corinthians 7 passage, the only definite benefit is that a marriage partner provides an outlet for the sexuality of those of us who cannot remain celibate.
Rather than looking at the matter quite so narrowly, let's extrapolate a bit and consider Ephesians 5:21-33:
21 Submit to one another out of reverence for Christ.
22 Wives, submit yourselves to your own husbands as you do to the Lord. 23 For the husband is the head of the wife as Christ is the head of the church, his body, of which he is the Savior. 24 Now as the church submits to Christ, so also wives should submit to their husbands in everything.
25 Husbands, love your wives, just as Christ loved the church and gave himself up for her 26 to make her holy, cleansing[b] her by the washing with water through the word, 27 and to present her to himself as a radiant church, without stain or wrinkle or any other blemish, but holy and blameless. 28 In this same way, husbands ought to love their wives as their own bodies. He who loves his wife loves himself. 29 After all, no one ever hated their own body, but they feed and care for their body, just as Christ does the church-- 30 for we are members of his body. 31 "For this reason a man will leave his father and mother and be united to his wife, and the two will become one flesh."[c] 32 This is a profound mystery--but I am talking about Christ and the church. 33 However, each one of you also must love his wife as he loves himself, and the wife must respect her husband.
In Ephesians we see marriage used as an illustration of Christ's relationship to the church: love and submission; sacrifice and cleansing; holiness. Combined with the emphasis on sexual purity from 1 Corinthians 7 I think we're starting to form a complete picture here.
God intends for marriage to make us more like Christ. Marriage isn't about "happiness" in any earthly sense, it's about holiness. Holiness might make us happy, or it might make us martyrs. Whether we live or die, holiness will bring us love, joy, peace, forbearance, kindness, goodness, faithfulness, gentleness and self-control. If you don't find God growing those fruits in your life through your marriage, then pray for holiness. God is far more concerned with our holiness than with our happiness.