She had been married for 20 years but after sex she would go and spend time by herself so her husband didn't see her crying.
It wasn't that the sex or relationship was bad, Dr Robert Schweitzer explains of the woman.
Rather, Schweitzer, a professor of psychology and counselling at Queensland's University of Technology, says she is one of many women who feel down and out after sex.
In fact, nearly half (46 per cent) of all women have experienced post-sex sadness – in the form of tears, depression or irritability, according to a new study conducted by Schweitzer.
While the study was small, with only 230 female participants, the findings echo research from earlier this year.
The previous study that looked at women and men across four different countries (Brazil, Canada, Norway and America), they found similar statistics across the board.
The female participants 'sometimes' experienced post-coital blues about 40 per cent of the time and 'often' experience it about 10 to 20 per cent of the time.
The statistics for the male participants were not dissimilar, but they experienced negative emotions after sex for vastly different reasons.
The women tended to feel vulnerable, remorseful or 'needy' while the men felt irritated or unattracted to their sexual partner, what researchers refer to as 'avoidance' negative postcoital emotions (NPE).
The results, the researchers hypothesise, are related to evolutionary function: the man's perception of his partner's sexual attractiveness can change for the worse (particularly in those who have had the greatest number of sex partners) to reduce the risk of him "making maladaptive commitments, and it is an integral part of male short-term mating psychology".
The females, on the other hand, tended to feel emotional after one-night stands where they anticipated rejection.
Evolutionarily-speaking, the emotional shift gives them the "motivation needed to pursue long-term commitment, as a way of gaining access to resources and paternal care for her offspring", the researchers said.
Although, the research, conducted by Brazilian psychologists, looked at short-term relationships or one night stands, NPE (or postcoital dysphoria PCD as it is sometimes referred to) can happen in intimate, long-term relationships too, as Schweitzer's research shows.
"There appears to be no relationship between PCD and intimacy in close relationships," he said in the study.
He suggests that some form of separation anxiety – where women feel sad following the sense of closeness and connection with their partners – may help to explain it. Similarly, he says a history of abuse can predict negative emotions after sex, but is "not the whole story".
This sort of PCD is "much more common" with women, he says, noting he knows of only one man who has experienced it.
"We are told that the experience of sex is always positive," Schweitzer says. "All we know is that some women seem to be more vulnerable [to feeling negative afterwards].
"I think there is something about sense of self. We give up our sense of self during sex – that's part of the experience, but some women find it terrifying."
For those women who do, he says it's "important not to pathologise it". It is a natural sensation that many women feel, to some degree or other at some point.
