The title for this post might conjure up many themes in regard to the unity that is supposed to obtain between a husband and a wife. But right now I want to mention only one (and admittedly not the most important): finances.
It seems to be a growing characteristic among married couples to maintain financial independence from each other after they get married. I see this as a serious problem.
When a man and a woman marry, at least in the Catholic understanding of marriage, the two become one. This does not just pertain to sexual union. Their lives are to be united together in an especially close and intimate way until death--a closeness of unity that is unique to marriage. Each spouse is called to grow, with the help of God's grace, more and more able to give selflessly to the other for the duration of their marriage. They are to form a single home. Without losing their personal dignity (indeed, in a way that enhances their dignity as one who relates deeply and profoundly with another), they belong to each other.
Personally, I do not understand why a couple who truly desire to be united to each other in the sacrament of marriage would plan to deliberately keep their finances apart from each other. Why would one spouse who earns a paycheck not want the other spouse to have access to that money? Why would one spouse think of income as his or her private funds as an individual, rather than theirs--collectively--theirs as a husband-wife union? Are there husbands out there who do not want to support their wives with the money that they earn? Or, if the wife is the primary breadwinner, likewise for them? If there are, I would suggest they either do not truly want to be married, or, they don't understand what marital union truly means.
What is one spouse saying to the other if each one intends to keep his or her money carefully segregated from the other? It's as if they are saying to each other from the start, "I'm committed to you, but not completely. I reserve the right to make it easier for me to break apart and leave. I don't intend, necessarily, to be committed to our union 'til death do us part. I am not committed to unconditional mutual support for each other when it comes to money."
I suspect that the growing practice of cohabitation before marriage contributes to this. Before marriage, a cohabiting couple naturally have independent financial lives. When they marry it is easy for them simply to continue this segregation because they have gotten used to living as though they were married, but without truly being so. Their union was not complete. And so after they marry they are already in a habit of living together but remaining separate financially. They unite, but not fully. They keep a part of themselves back from their union (just as they have already been doing).
But in some respects this is not surprising. Why should a couple who has been cohabiting, and thus become comfortable with living only as a partial union though under the same roof, not be comfortable continuing this same pattern of partial union when they marry? That the "two become one flesh" is now qualified by many footnotes has become accepted long before the marriage vows are made.