Edna St. Vincent Millay Quote

But you are mobile as the veering air,
And all your charms more changeful than the tide,
Wherefore to be inconstant is no care:
I have but to continue at your side.
So wanton, light and false, my love, are you,
I am most faithless when I most am true.

From Sonnet III: "Oh, Think not I am faithful to a vow!", A Few Figs from Thistles (1922)