... is the title of a book by Marnia Robinson. She uses an understanding of neurochemistry to explain how and why romantic love doesn't seem to last. Her book prescribes three weeks of activities to help couples change the chemical dynamics of their relationship.
In her blog, Reuniting, she talks about the "Coolidge Effect": A male rat will copulate madly with a receptive female, but then tire. Yet, if a new female is introduced, his vigor returns.
Her basic premise is that people should learn to make love differently, with an emphasis on activities that produce lots of oxytocin, rather than overstimulating the reward/pleasure centers of the brain.
This interview between Robinson and reviewer Rebecca Brown of Rebecca's Reads gives some of Robinson's ideas, for example,
I guess we figured the boys were really on to something with the “frequent-orgasm program” so often attributed to them. But by imitating them, we've simply been repeating their fundamental error of believing the point of having genitals was orgasm, rather than union. Over-stimulation of the pleasure/reward center doesn't bring out the best in men or women; it leads to separation.