This is a subject that frightens me. When I think of who 'myself' is, I think of my mind. I am a mind; my mind is my essence. I can imagine being me in another body, or in an artificial body that's nothing like human. I can imagine being moved to a situation like that, and still being me.
But what that means is that it's exceptionally terrifying to think about losing that self, having it be impaired. Or losing none of it, but losing the physical ability to express it. I can't decide whether I think Hirshfield's interpretation of Alzheimers (holes, blockages, but the essence still there) is right or not - I feel sure science doesn't know the answer, either. But more than that, I can't decide which interpretation is more frightening: to lose myself, or to be myself but not be able to show it.
The last line of the poem is an interesting reference. "Contrary to Keatsian joy" is surely meant to invoke this passage from Endymion:
A thing of beauty is a joy for ever:
Its loveliness increases; it will never
Pass into nothingness; but still will keep
A bower quiet for us, and a sleep
Full of sweet dreams, and health, and quiet breathing
I think this is why I feel such an urge to create tangible things, to write. Because there is this sense that if I can create a thing of beauty, it means that I will have created something that lives on after the thing that makes me myself has gone. But the man in the poem is "contrary" to Keatsian joy - perhaps denying it, perhaps proving it false simply by being what he is - and I think maybe he has the right of it. Maybe a fine old carpet with holes chewed in it ceases to be a carpet and becomes only a rag. I don't think that makes it any less beautiful when it is whole. Maybe more beautiful, for being something that only lasts so long.