Science has bad news for long-term couples that wholeheartedly believe that good relationships equal good sex. Both inside and outside of bed, a new study in the Journal of Personality and Social Psychology reports, good things only come to those who work.

The idea that people can be “meant for each other,” romantically and sexually, is a logical fallacy, borne out of decades of classically over-idealistic rom-coms like Four Weddings and a Funeral and Bridget Jones’s Diary, where sparks on a first date inevitably lead to flames in the bedroom. The study of 1,900 participants, carried out by researchers at the University of Toronto, has bad news for couples who engage in such lazy fantasies: Having high “sexpectations,” as the researchers call them, will only set you and your partner up for disappointment.

Good relationships don't always mean good sex.
Good relationships don't always mean good sex.

“People who believe in sexual destiny are using their sex life as a barometer for how well their relationship is doing, and they believe problems in the bedroom equal problems in the relationship as a whole,” said Jessica Maxwell, the Ph.D. candidate at the University of Toronto Department of Psychology who led the study, in a release. The concept of “sexual destiny” is what psychologists call an “implicit belief” — a mental association that’s deeply rooted in our psyches, sometimes to the point that we’re not always aware that they exist. In this case, the researchers argue that this particular implicit belief, which illogically links sexual satisfaction and the idea of a “sexually compatible” partner, isn’t just wrong but can be detrimental to couples in the long run.

There are actually two types of people, the researchers say:

Individuals high in sexual growth beliefs think that sexual satisfaction is attained from hard work and effort, whereas individuals high in sexual destiny beliefs think that sexual satisfaction is attained through finding a compatible sexual partner.

The latter kind of person, their study of both heterosexual and same-sex couples found, shoots themselves in the foot when they congratulate themselves on having found their so-called sexual soulmate. While the authors concede that there is a “honeymoon” phase that lasts two to three years — when the sex is going to be pretty great regardless — in the long run, belief in “sexual destiny” can thwart improvement in the bedroom when things suddenly (and inevitably) go limp. That’s because these people tend to use the quality of their sex life as a barometer for how good the relationship is overall; if the sex suddenly takes a turn for the worse, the blame isn’t put on lack of effort — it’s put on the relationship itself.

Meanwhile, people who believe that sex, like a relationship, can be improved by working at it are much more likely to actually see improvements in the bedroom. “We know that disagreements in the sexual domain are somewhat inevitable over time,” says Maxwell. “Your sex life is like a garden, and it needs to be watered and nurtured to maintain it.”