Women dream of eternal love, so be consistent.

from Life, Letters, and Epicurean Philosophy by Ninon de l'Enclos nonfiction ~5 min read

At last, Marquis, you are listened to dispassionately when you protest your love, and swear by everything lovers hold sacred that you will always love. Will you believe my predictions another time? However, you would be better treated if you were more reasonable, so you are told, and limit your sentiments to simple friendship. The name of lover assumed by you is revolting to the Countess. You should never quarrel over quality when it is the same under any name, and follow the advice Madame de la Sablière gives you in the following madrigal:

Bélise ne veut point d'amant,
Mais voudrait un ami fidèle,
Qui pour elle eût des soins et de l'empressement,
Et qui même la trouvât belle.
Amants, qui soupirez pour elle,
Sur ma parole tenez bon,
Bélise de l'amour ne hait que le nom.

(Bélise for a lover sighed not,
But she wanted a faithful friend,
Who would cuddle her up and care for her lot,
And even her beauty defend.
Oh, you lovers, whose sighs I commend,
'Pon my word, hold fast to such game,
What of love Bélise hates is only the name.)

But you are grieved by the injurious doubts cast upon your sincerity and constancy. You are disbelieved because all men are false and perjured, and because they are inconstant, love is withheld. How fortunate you are! How little the Countess knows her own heart, if she expects to persuade you of her indifference in that fashion! Do you wish me to place a true value on the talk she is giving you? She is very much affected by the passion you exhibit for her, but the warnings and sorrows of her friends have convinced her that the protestations of men are generally false. I do not conceive any injustice in this, for I, who do not flatter men willingly, am persuaded that they are usually sincere on such occasions. They become amorous of a woman, that is they experience the desire of possession. The enchanting image of that possession bewitches them; they calculate that the delights connected with it will never end; they do not imagine that the fire which consumes them can ever weaken or die out; such a thing seems impossible to them. Hence they swear with the best faith in the world to love us always; and to cast a doubt upon their sincerity would be inflicting a mortal injury.

But the poor fellows make more promises than they can keep. They do not perceive that their heart has not enough energy always to hold the same object. They cease to love without knowing why. They are good enough to be scrupulous over their growing coldness. Long after love has fled they continue to insist that they still love. They exert themselves to no purpose, and after having tormented themselves as long as they can bear it, they surrender to dissatisfaction, and become inconstant with as much good faith as they possessed when they protested that they would be forever constant. Nothing is simpler and easier to explain. The fermentation of a budding love, excited in their heart the charm that seduced them; by and by, the enchantment is dispelled, and nonchalance follows. With what can they be charged? They counted upon keeping their vows. Dear me, how many women are too happy with what is lacking, since men give them a free rein to their lightness!

However this may be, the Countess has charged up to you the inconstancy of your equals; she apprehends that you are no better than all other lovers. Ready to yield to you, however little you may be able to reassure her, she is trying to find reasons for believing you sincere. The love you protest for her does not offend her. What am I saying? It enchants her. She is so much flattered by it, that her sole fear is that it may not be true. Dissipate her alarms, show her that the happiness you offer her and of which she knows the price, is not an imaginary happiness. Go farther; persuade her that she will enjoy it forever, and her resistance will disappear, her doubts will vanish, and she will seize upon everything that will destroy her suspicions and uncertainty. She would have already believed you; already she would have resolved to yield to the pleasure of being loved, if she had believed herself really loved, and that it would last forever.

How maladroit women are if they imagine that by their fears and their doubts of the sincerity and constancy of men, they can make any one believe they are fleeing from love, or despise it! As soon as they fear they will be deceived in the enjoyment of its pleasures; when they fear they will not long enjoy it, they already know the charms of it, and the only source of anxiety then is, that they will be deprived of its enjoyment too soon. Forever haunted by this fear, and attacked by the powerful inclination toward pleasure, they hesitate, they tremble with the apprehension that they will not be permitted to enjoy it but just long enough to make the privation of it more painful. Hence, Marquis, you may very easily conjecture a woman who talks to you as does the Countess, using this language:

"I can imagine all the delights of love. The idea I have formed of it is quite seductive. Do you think that deep in my heart I desire to enjoy its charms less than you? But the more its image is ravishing to my imagination, the more I fear it is not real, and I refuse to yield to it lest my happiness be too soon destroyed. Ah, if I could only hope that my happiness might endure, how feeble would be my resistance? But will you not abuse my credulity? Will you not some day punish me for having had too much confidence in you? At least is that day very far off? Ah, if I could hope to gather perpetually the fruits of the sacrifice I am making of my repose for your sake, I confess it frankly, we would soon be in accord."

—Ninon de l'Enclos, Life, Letters, and Epicurean Philosophy, p. -1