In the poem "Unveiling" Pastan is speaking of a person walking through a cemetery walking down their "family's row." The way the family is arranged in the cemetery reminds him of how the family used to sit around the table for family dinners.

In the last sentence, while walking he says, "I don't feel sad for them, just left out a bit as if they kept from me the kind of grown-up secret they used to share back then, something I'm not quite ready yet to learn." He's saying that there's something that he doesn't understand that he wishes someone had told him about. I think the narrator is possibly speaking about death. He doesn't understand death. The narrator knows he doesn't understand, and in the line "I'm not quite ready yet to learn" he is not yet ready to understand the situations of death and what is to come.