I could not tell the Date of Mine—It feels so old a pain— (7-8)
In these lines, the speaker captures the way that grief can feel like it has lasted a lifetime. It seems like her suffering wasn't brought about by some event—it's more like depression, or some internal emotional problem that's hard to pin down.
I wonder if it hurts to live—And if They have to try— (9-10)
Hmm. Could the speaker be projecting here? It sure sounds like it. Of course it's couched in speculative language—she wonders—but Shmoop can't help but wonder if she isn't talking about herself here. Does she have to try?
I wonder if when Years have piled—Some Thousands—on the Harm— (17-18)
Here the speaker uses time to describe what extreme suffering feels like. While the poem began with diction suggesting precision and exactness, it ends up using hyperbole to express what suffering feels like to the person experiencing it. So the poem is less concerned with a scientific approach to sadness, but more an emotional, exaggerated account of what it feels like.