In Armenian, one way to describe a significant unit is "իմ չարս." It means "person I'm striving toward."
To me, that means this is someone whose qualities you are learning from, qualities with which you are striving to better yourself. It can also mean someone whose love you are striving to earn, which, even years into a relationship (from my relatively little experience) we still ought to try to do.
Reading all the married hubsquids' comments though, a marriage sounds a lot more like a contractual work order where both parties are simply doing their jobs. I imagine it's because your spouse-ly duties are what remain important in maintaining trust and a healthy relationship when infatuation fades, and what-not.