To understand what is meant by repentance in this context, let's expand for a moment one of the spiritual benefits of marriage. For marriage can certainly help us perceive the "exceeding sinfulness of sin" (Rom 7:13) more quickly.
When I was single and chose to sin, I was only hurting myself (or so it seemed). If I wanted to get drunk, I could just live with the hangover the next day. If I wanted to overspend, I could just live with the credit card consequences. And so forth. This is an illusion, really, for if I am a Christian I have brought these sins "into the camp" (Joshua 7) of the fellowship of the saints, and even if we are spiritually blind to this we can certainly see that we are causing direct pain to Christ in any case. But it is a powerful illusion, it must be admitted.
But now, as married, I can see the consequences of my sin most vividly. If I get drunk, I might say or do ugly things when I get home. If I overspend, I am dragging my spouse and entire household into the repercussions of my sin. And so forth.
Thus, marriage can put us on the spiritual fast-track in terms of breaking with clear sin. Marriage tends to turn up the fire of sanctification underneath us, if we will let it.
We all bring sin into marriage, and it must be dealt with in marriage sooner rather than later. If I can see that my spouse needs this treatment as much as I do, then by God's grace I can gain skill at dealing with sin issues as they come up with gentleness and clarity, knowing that I may well be next in needing to repent.
Since we all are prone to slip into sin, rather than escalate hostilities or go nuclear or threaten such, have we really tried the way of the Lord? For in marriage, we cannot "get away with" sinning in the dark so easily, we are going to see in plain fact the consequences effecting those we love. Hidden actions will play out very quickly into open life. Given this, let us learn to be "quick-studies" in repentance and reconciliation, rather than revengeful power players. Let us understand how to help our spouses towards repentance from sin, rather than "get back at them".
Col 3:12-16 (NIV) Therefore, as God's chosen people, holy and dearly loved, clothe yourselves with compassion, kindness, humility, gentleness and patience. Bear with each other and forgive whatever grievances you may have against one another. Forgive as the Lord forgave you. And over all these virtues put on love, which binds them all together in perfect unity. Let the peace of Christ rule in your hearts, since as members of one body you were called to peace. And be thankful. Let the word of Christ dwell in you richly as you teach and admonish one another with all wisdom, and as you sing psalms, hymns and spiritual songs with gratitude in your hearts to God.
Eph 4:29-5:2 (NIV) Do not let any unwholesome talk come out of your mouths, but only what is helpful for building others up according to their needs, that it may benefit those who listen. And do not grieve the Holy Spirit of God, with whom you were sealed for the day of redemption. Get rid of all bitterness, rage and anger, brawling and slander, along with every form of malice. Be kind and compassionate to one another, forgiving each other, just as in Christ God forgave you. Be imitators of God, therefore, as dearly loved children and live a life of love, just as Christ loved us and gave himself up for us as a fragrant offering and sacrifice to God.
James 1:19-22 (NIV) My dear brothers, take note of this: Everyone should be quick to listen, slow to speak and slow to become angry, for man's anger does not bring about the righteous life that God desires. Therefore, get rid of all moral filth and the evil that is so prevalent, and humbly accept the word planted in you, which can save you. Do not merely listen to the word, and so deceive yourselves. Do what it says.