From Willard F. Harley via our buddy Bowden, at Counseling Notes
When a couple live together before marriage, they tend to be “renters.” By that I mean that they view their relationship much as they would renting an apartment. If something goes wrong in an apartment, the landlord is expected to fix it — if it needs paint, the landlord paints it; if it needs repairs, the landlord does the repairing. In other words, the renter is not responsible for making the apartment suitable for living — the landlord is responsible. And if the apartment is not repaired, the tenant isn’t expected to fix the apartment himself, he simply moves to another apartment if he doesn’t like the one he is renting.
On the other hand, when couples marry before they live together, they tend to be “buyers.” Much like buying a house, these couples realize that if anything needs fixing, they will have to fix it — the sooner, the better. Their marriage is not a test of how livable their relationship is, but rather, it’s a commitment to make their relationship livable. That means that when a problem first surfaces, they go right to work fixing it, knowing that if they don’t fix it soon, it can lead to an even bigger problem later.

