It's a family affair, guys. The speaker of "Digging" struggles with his identity in relationship to his family. His father and grandfather were farmers and they valued manual labor. The speaker, however, is a writer, and has chosen that line of work. So where exactly does he fit in? Well, for most of the poem, it seems like he doesn't. He remembers his father and grandfather in the potato field and peat bog, and it seems like these memories played a huge role in his identity growing up. But then, he admits that he's not like them. Not until the end of the poem do we finally get a glimpse at how the speaker discovers that his writing is, in certain ways, similar to his father and grandfather's work. By the end of "Digging," the speaker seems more confident in who he is and what he does. He remembers his roots, but is striking out on his own.
The speaker is confused about who he is as person, because his work is so different from his father's and grandfather's.
The speaker has discovered his identity through writing. Sweet!