At the dentist

As I walk through Greenwich Park after the best part of an hour in the dentist's chair, I am thinking of the poem I always repeat to myself while my teeth are being drilled:

I never did belong to that great sect
Whose doctrine is that each one should select
Out of the rest a mistress or a friend
And all the rest, though fair and wise, comment
To cold oblivion, though it is the code
Of modern morals, and the beaten road
Which those poor slaves with weary footsteps tread
Who travel to their homes among the dead
By the broad highway of the world, and so
With one sad friend, perhaps a jealous foe,
The dreariest and the longest journey go.

Is it Shelley? I no longer know whether I like the sentiment or not. But thinking of it now, I remember coming across these lines as a teenager in Forster's The Longest Journey, a book I then loved, though I doubt if I understood it. I recall lying in bed in my grandmother's house, insomniac, reading the novel and these lines to memory.

I haven't read Forster for years. And yet, every time I visit the dentist, I find myself using these lines as a distraction from the pain.