"Between two evils, I always pick the one I never tried before." Mae West

"Jewish women do not believe in sex after marriage." (From the movie, Suzie Gold)

Emotions typically occur when we perceive significant changes in our personal situation. Like burglar alarms going off when an intruder appears, emotions signal that something needs attention. We respond to the unusual by paying attention to it. A change cannot persist for a very long time; after a while, the system construes the change as a normal state and it excites us no more.

Indeed, sexual response to a familiar partner is less intense than to a novel partner. On successive occasions we adapt to the event and the experience yields less pleasure; Daniel Gilbert ironically notes that psychologists "call this habituation, economists call it declining marginal utility, and the rest of us call it marriage." In fact, the frequency of sexual activity with one's partner declines steadily as the relationship lengthens, reaching roughly half the frequency after one year of marriage compared to the first month of marriage, and declining more gradually thereafter. Decline has also been found in cohabiting, heterosexual couples and in gay and lesbian couples (The Subtlety of Emotions).

A survey of people after heart attacks indicates that these people should not avoid sex. Among 5559 cases of sudden death, only 18 were related to sexual activity. But among the 18 cases, 14 occurred while having extramarital sex. The excitement of extramarital sex was too much for them. The moral for heart patients, as well as other people, seems to be quite straightforward: If you want safe sexual relations, stick to your partner; however, if you are looking for excitement, then changing your partner may provide what you need.

In this context, there is an amusing story about the American president, Calvin Coolidge, who once visited a farm with his wife. Soon after their arrival, they were taken off on separate tours. When Mrs. Coolidge passed the chicken pens, she paused to ask the man in charge if the rooster copulates more than once each day. "Dozens of times," was the reply. "Please tell that to the President," Mrs. Coolidge requested. When the President passed the pens and was told about the rooster, he asked: "Same hen every time?" "Oh no, Mr. President, a different one each time." The President nodded slowly, then said, "Tell that to Mrs. Coolidge." In light of this story, the expression "The Coolidge Effect" was coined for the phenomenon of male re-arousal by a new female. The Coolidge effect is widespread among mammals.

Modern society, with the encouragement of the advertisement industry, promotes changes to an extreme. Thus, it is told of the mythological editor of Vogue magazine, Anna Wintour, that she never wears an item of last year's fashion nor does she wear the same item twice. One needn’t be a devoted follower of the fashion world to easily translate such transitory values into the romantic realm and continually look for a constant change in this realm as well.

Due to the crucial role of change in generating emotions the alliance between passionate romantic love and a committed relationship is problematic. The delight experienced initially as the change of falling in love is difficult to sustain in long-term relationships, as the impact of reality and routines is often devastating.

Although emotions typically arise when we perceive significant changes in our situation, an event can be perceived as a significant change only when compared with a stable background or framework. Not only change, but also stability, and in particular familiarity, increase emotional intensity: the familiar person is emotionally closer than the stranger. The positive role of familiarity may lead love to grow and become deeper over time. The unique combination of change, which is related to excitement and risk, and stability, which is related to commitment and security, is crucial for emotional excitement.

The complexity of the object is an important factor in determining whether love will be more or less intense as a result of greater familiarity: a simple psychological object is liked less with exposure, while a complex object is liked more. Romantic love refers to a complex psychological personality, with numerous aspects, whereas sexual desire refers to a few, mainly external, aspects. Accordingly, sexual desire is considerably increased by replacing the object as too much familiarity may decrease sexual excitement and produce boredom. In contrast, increasing the intensity of love often involves increasing familiarity with the object. Replacing the object is often a temporary and elusive remedy for love. An indication of this is that very few people, who leave their marriage for a lover, eventually remain with that lover. Novelty has a less significant role in love than in sexual desire, since love is a longer lasting and more profound relationship; as such, it must be related to more permanent features.

The role of complexity in romantic relationship is expressed in the following claim by Nina, a married woman, who describes her relationship with her lover: "I truly believe that even if we would spend together every minute of the day and the night for the rest of our lives we would tell each other new things, also about each other, all the time. I think that even if the familiar part becomes bigger, which is inevitable, the new part will always be endless and hence even greater than the familiar one." (cited in In the Name of Love: Romantic Ideology and its Victims)

The tension between stable boundaries, which secure our comfort zones and within which events are familiar and predictable, and the wish to experience novelty, which is typically generated by stepping beyond these boundaries, is an essential feature of human life and the experience of love; this is also the tension between the ideals of freedom and commitment. Although "looking elsewhere" is typically perceived as a response to dissatisfaction, it may also exist in a generally satisfying relationship. Pursuing a limited type of change can be compatible with satisfaction from a current stable framework, and may prevent its deterioration.