Do not be daunted by the enormity of the world’s grief.
Do justly, now.
Love mercy, now.
Walk humbly, now.
You are not obligated to complete the work,
but neither are you free to abandon it.
[Talmud]

This is the third section in Chesterton’s poem “Variations on an Air,” which is first a parody of Tennyson, then of Yeats, and then of Whitman:

Me clairvoyant,
Me conscious of you, old camarado,
Needing no telescope, lorgnette, field-glass, opera-glass, myopic pince-nez,
Me piercing two thousand years with eye naked and not ashamed;
The crown cannot hide you from me,
Musty old feudal-heraldic trappings cannot hide you from me,
I perceive that you drink.
(I am drinking with you. I am as drunk as you are.)
I see you are inhaling tobacco, puffing, smoking, spitting
(I do not object to your spitting),
You prophetic of American largeness,
You anticipating the broad masculine manners of these States;
I see in you also there are movements, tremors, tears, desire for the melodious,
I salute your three violinists, endlessly making vibrations,
Rigid, relentless, capable of going on for ever;
They play my accompaniment; but I shall take no notice of any accompaniment
I myself am a complete orchestra.
So long.