The sentiment "and they lived happily ever after" never seems to include the how.

How did they live happily ever after when happiness can be so fleeting and relative? Books have been written, movies have been made, songs, seminars and more have been created around this central idea of how to achieve happiness.

Christians, however, aren’t called to be happy. We’re called to serve as Christ served. And for those who are married, the call to serve your spouse is even greater.

What Christian marriage looks like

After all, marriage was created by God, instituted by Him to reflect His own relationship not only between Christ and the Church, but also within the Trinity.

Husbands are called to lay down their lives for their wives – just as Christ laid down his life for the Church. And wives are called to submit to their husbands – just as Christ submitted to the will of His Father, and just as the Church follows that Christlike example by submitting to Jesus.

"Both women and men get to ‘play the Jesus role’ in marriage – Jesus in his sacrificial authority, Jesus in his sacrificial submission," Kathy Keller explains in The Meaning of Marriage.

Sacrificially submitting to and serving one another is hardly what our culture talks about when they refer to "happily ever after," but the proven by-product of such sacrifice is, in fact, happiness.

"The deep happiness that marriage can bring, then, lies on the far side of sacrificial service in the power of the Spirit," Timothy Keller writes in The Meaning of Marriage. "That is, you only discover your own happiness after each of you has put the happiness of your spouse ahead of your own, in a sustained way, in response to what Jesus has done for you . . . It is the joy that comes from giving joy, from loving another person in a costly way."

The cost of self-centredness

However, Keller explains, the problem is that the "main barrier to the development of a servant heart in marriage is . . . self-centeredness." In the oft-quoted 1 Corinthians 13, Paul describes love as "not self-seeking" – it does not put itself first.

"Self-centeredness," Keller continues, "is easily seen in the signs Paul lists: impatience, irritability, a lack of graciousness and kindness in speech, envious brooding on the better situations of others, and holding past injuries and hurt against others."

There’s a reason Keller notes that you have to serve your spouse "in a sustained way." The sustenance can come only from God.

"If I look to my marriage to fill the God-sized spiritual vacuum in my heart, I will not be in position to serve my spouse," he explains. "Only God can fill a God-sized hole. Until God has the proper place in my life, I will always be complaining that my spouse is not loving me well enough, not respecting me enough, not supporting me enough."

The power of the Gospel

But once you realize that God is the one who will be fulfilling your needs and God is the one to whom you look for sustenance, you will be better equipped to serve your spouse. No longer will it be what Keller refers to as a "consumer relationship" of "I’ll serve her if she serves me." It then becomes "I’ll serve her because Christ served me."

And that’s where the true power of the gospel lies – "that through marriage, ‘the mystery of the gospel is unveiled.’ Marriage is a major vehicle for the gospel’s remaking of your heart from the inside out and your life from the ground up."

But how is this practically seen in the day-to-day? According to Keller, this remaking is seen in the continual combination of three things: the power of truth, the power of love and the power of grace.

1. Power of truth

"Marriage by its very nature has the ‘power of truth’ – the power to show you the truth about who you are," Keller explains. This can be a discouraging and even frightening concept. The sheen that we put on during our dating and newlywed years wears off and the truth of ourselves is plain to see – for both our spouse and ourselves.

But this needn’t be a bad thing – in fact, it’s the very thing that will remake us into the person God desires us to be. That’s the gift of marriage. While some may be tempted to look for someone better after that sheen wears off, Christians know that person is their spouse.

"The someone better is the spouse you already have," Keller writes. "God has indeed given us a desire for the perfect spouse, but you should seek it in the one to whom you’re married."

2. Power of love

While the power of truth seems like a good thing in theory, in practice it can often be hurtful – if truth is shared separate from love. One of the best ways to show your love to your spouse is to learn how they see and receive love. Become a student of your spouse’s love language and learn how to "communicate love in the way [y]our spouse needs it."

"The point is this – truth and love need to be kept together, but it is very hard," Keller continues. "We need to feel so loved by our partners that when they criticize us, we have the security to admit our faults. Then we can come to know and face who we are and grow."

3. Power of grace

Truth and love are powerful when kept together, but keeping them together is what so many of us struggle with. The solution, Keller notes, is found once again in Christ:

"Truth without love ruins the oneness, and love without truth gives the illusion of unity but actually stops the journey and the growth. The solution is grace. The experience of Jesus’ grace makes it possible to practice the two most important skills in marriage: forgiveness and repentance. Only if we are very good at forgiving and very good at repenting can truth and love be kept together."

When we recognize the true meaning of marriage, Kathy and Timothy Keller explain – when we see the true gift of the healing and remaking process that God created in this institution – we can then use it to become our best selves and therefore show God’s glory through this profound relationship of marriage.

And the path to this kind of reflection of His glory is by reflecting His attitude of service.

In a Focus on the Family broadcast entitled "Becoming the Family You Want to Be," Gary Chapman explains that about three years into his marriage, he felt God convict him of demanding service from his wife instead of acting in service toward her. "And I just said, ‘God forgive me’ . . . And then I said, ‘Please give me the attitude of Christ toward my wife,’" he recalls. "In retrospect, [it was] the greatest prayer I ever prayed regarding my marriage, because God changed my heart and gave me a desire to serve her."

"Marriage has unique power to show us the truth of who we really are," Keller writes. "Marriage has unique power to redeem our past and heal our self-image through love. And marriage has unique power to show us the grace of what God did for us in Jesus Christ."