And what are you that, missing you,
I should be kept awake
As many nights as there are days
With weeping for your sake?

Edna St. Vincent Millay (1892-1950) American poet

Poem (1921-10-31), “The Philosopher,” st. 1, Ainslee’s Magazine, Vol. 48, No. 3
    (Source)

First collected in A Few Figs from Thistles (1922).