An imagined "marriage" can become an idol, an 'end' in itself. Then one tries to find a person (a means) who can get you that imagined thing (an end). When they don't, they get tossed. It's the reverse: the person comes first and is the 'end' -- "how do I get more of you?" -- marriage is that means to fuller commitment with *that person*. And vows are made because it's not easy, and there's temptation to give up. But ultimately, it's not even about us: [Eph. 5:25-32](https://esv.org/eph+5) (esp. verse 32).