In "I cannot live with You—," the speaker perceives a vast, unbridgeable distance between herself and her beloved. It isn't a physical distance, to be sure, but a spiritual one. The speaker cannot accept her beloved's religious worldview, which would include their being together in the afterlife.

As the speaker is at pains to point out, even after their deaths, it would still be impossible for them to be together for one reason or another. For one thing, if the speaker and her beloved were raised together in the final resurrection, then her beloved's face would outshine Jesus's,and it clearly wouldn't be right for Jesus to be upstaged like this.

In fact, the speaker finds the whole idea of resurrection rather foreign, to say the least. Her "homesick eye" is firmly focused on this mortal world, the world of the here and now. Besides, she doesn't feel worthy of her beloved, because, unlike him, she cannot serve heaven:

They'd judge Us—How—
For You—served Heaven—You know,
Or sought to—
I could not—

In case she hadn't made her case abundantly clear, the speaker is telling her beloved that the distance between them is just too great and describing the kind of distance by which vast oceans separate people and the distance between ourselves and God represented by the act of prayer.