But scientists claim that that might not actually be true.
A new study published in the journal Archives of Sexual Behaviour suggests that having sex with an ex doesn't actually stop you from moving on after all.
And that's even true for those of us who still pine for our old partners.
Lead author Stephanie Spielmann, of Wayne State University in the USA, has been studying the effects of bedding an ex in an attempt to work out why so many of us – regardless of age and sexuality – do it.
She and her colleagues conducted two studies.
The first looked at the daily experiences of 113 people who had recently gone through a breakup.
After two months, they completed another online survey which asked them if they'd tried to have physical contact with their former partners, how emotionally attached they still were and how they felt after each day.
The second study got 372 people to report their actual and attempted sexual engagement with their ex, as well as whether they were still emotionally attached to them.
And scientists found that pursuing sex with an ex didn't stop them from then getting over the breakup.
Even the people who said they pined after their old partners weren't left distressed or depressed. In fact, scientists say that it left them feeling more positive about life.
"This research suggests that societal handwringing regarding trying to have sex with an ex may not be warranted," said Spielmann.
"The fact that sex with an ex is found to be most eagerly pursued by those having difficulty moving on, suggests that we should perhaps instead more critically evaluate people's motivations behind pursuing sex with an ex."
Spielmann says that her findings illustrate the need to explore breakups more in the future because of the impact they can have on mental health and recovery.
It's worth pointing out of course that these studies were performed on pretty small sample sizes and were reliant on self-reporting. There is a possibility that people wouldn't' be so open about a totally soul-destroying sexual encounter with an ex for fear of embarrassment.
But nevertheless, if ever there was an excuse to finally put old ghosts to bed, this is it.