According to the Christian Orthodox faith, the goal of marriage is spiritual perfection of the spouse - not to be "happy." Marriage is to serve another. Marriage is the icon of Christ and His church, whereby Christ served the Church, and the Church serves Christ.
The question I have is, why on earth would anyone want to give of themselves to make someone else happy. Haven't we heard our whole lives that we need to make ourselves happy first, before we can make another person happy?
I think that its both. I think I'm better at giving more, because I know how to nourish myself, and I know what I need to feel nourished from my my husband. Although my husband was raised in the same church as I was, he isn't familiar with the specific lessons the church offers us as guidance for a successful partnership. I never want to push my beliefs of anyone else, but I do gently mention some of the things I have learned.
I'm convinced, after reading the teachings of St. John Chrysostom, that I wouldn't be able to have a successful marriage long term, if I didn't have faith that God will help us through the tough times, which are bound to present themselves.
I've read up on how the Early Christian church viewed marriage, and use that as a guide for our marriage. St. John Chrysostom, Of Marriage and Family Life is a great place to start.