From Wikipedia (http://en.wikipedia.org/wiki/Robert_Briffault#Briffault.27s_Law):

The female, not the male, determines all the conditions of the animal family. Where the female can derive no benefit from association with the male, no such association takes place. — Robert Briffault, The Mothers, Vol. I, p. 191

This means that your relationship is over when you stop providing value to her. It implies that no matter what you've provided in the past, when you stop providing, the relationship is over. It also implies that if you provide while banking on her promise to provide something in return in the future, the relationship will end when your turn to play provider comes to completion, in spite of her promise.

Here are two audio videos that flesh this out in greater detail:

And female hypergamy arises according to Briffault's Law.

Recall Glover's analysis of the Nice Guy:

Nice Guys give to get. Though Nice Guys tend to be generous givers, their giving often has unconscious and unspoken strings attached. They want to be appreciated, they want some kind of reciprocation, they want someone to stop being angry at them, etc. Nice Guys often report feeling frustrated or resentful as a result of giving so much while seemingly getting so little in return. (NMMNG 13)

This means that if you don't accept Briffault's Law as describing reality, you will end up resentful.

Recall Pook:

We no longer know the difference between SEX and STOCKS. “Did Pook say sex and stocks?” Yes. People view sex like some medium of exchange, something the more they make with a person, the more ‘votes’ and control they ought to get. Contrast this to stocks where people buy hoping the stocks get pregnant and reproduce. (BOP 253)

This means that if you don't accept Briffault's Law as describing reality, you will see sex as an investment. But because it's not an investment but a fungible token of no real value, it will not pan out, you will get no return on it, and when you finally read the ticker of your life you'll want to throw yourself off a building.

Finally Tomassi:

The fundamental flaw of the Savior Schema (also, Captain Save a Ho) is that it is essentially negotiated intimacy, and negotiated intimacy is never genuine. You can fix a woman’s flat tire, help her out of a financial jam, fix her a nice lasagne, give her the perfect shoulder to cry on, take care of her kids and listen to her drone on for hours on the phone, and she’ll still go fuck her outlaw biker boyfriend because her intimacy with him is genuine, unnegotiated, unobligated desire. She wants to have sex with him, she doesn’t owe him sex. [¶] ... The difficulties arise when (perhaps cleverly) women learned to covertly use this innate psychology of exchange within the context of a social framework that gives them a resource advantage for little or no exchange of their own. Thus women modeled a social norm, that mirrors men’s natural default position of disposability, and put their attentions and intimacies as unassailable resources so valuable that no effort on a man’s part can merit it. When a woman is appalled by the notion that she should be obligated to have sex with a man in exchange for a dinner and a movie (even over multiple occasions), this social convention is the root of that insult. (TRM 74)

This means that if you don't accept Briffault's Law as describing reality, you will do her favors and expect favors in return, but if the return favor is sex, she won't see it as a debt she is obliged to pay; the values you and she put on those favors are not the same, and there is no equity in the exchange.