There is a great section of scripture in Galatians 5. If married couples would apply this one principle in their relationship, it would go a long way toward having a great marriage.
It is Galatians 5:13 – 14. I particularly like the way it reads in the Amplified Bible.
“For you, brethren, were [indeed] called to freedom; only [do not let your] freedom be an incentive to your flesh and an opportunity or excuse [for selfishness], but through love you should serve one another. For the whole Law [concerning human relationships] is complied with in the one precept, You shall love your neighbor as [you do] yourself.”
Note the importance of this love – it fulfills the whole law concerning relationships. The New Testament was originally written in Greek, and the word translated as “love” in this scripture is the Greek word “agape”.
To apply this in your marriage, you need to understand what agape means. Agape is selfless and will go to any length to attain the well-being of its object (in going to any length, agape will, of course not do anything unscriptural, immoral, or illegal). It is based on a decision and a commitment rather than on feelings. It is a matter of the head more than of the heart. Agape desires to benefit others even at the expense of self, because it desires to give more than to get. Agape is unconditional love.
This is how God loves us, and it is how he wants us to love each other. If you want to see great things happen in your relationship, begin loving your spouse this way.