On the surface there's surely nothing better than sleeping with your ex. Not only does she know precisely what you want in bed (unless, of course, that's the reason you split in the first place), she also understands it's purely about sex, so the whole thing is totally free of any pesky relationship strings too! Right?
Er, wrong! No matter what you try to say, think or do, there's always a vast black cloud hovering over an ex-sex relationship: namely the fact that one of you dumped the other at some point in the not-so-distant past.
Unless by some miracle it was a mutual decision to go your separate ways, ex-sex inevitably arrives with a lorry load of meddlesome baggage.
Dealing with reality
In all likelihood, your ex-sex fling will place the 'dumper' in a position where they have more power within the rekindled relationship than the 'dumped'. Meanwhile, the dumped person will no doubt harbour all manner of psychological hang-ups, hurts and fleeting thoughts of revenge about the whole situation not to mention the hope that this time it might be different.
If there's one golden rule for ex-sex it is to be honest about what you want from the outset. If you are sleeping with your ex purely for the sex, then she needs to know it. If, on the other hand, you're hoping to sweep her off her feet, she needs to know that too.
That way everyone's cards are on the table at the start, so if things do go wrong - which, given your personal baggage, is highly likely it will not shatter either persons last remaining shred of self-esteem.
"Don't lose your honesty along with your trousers in the heat of the moment," advises UK-based relationship expert Dr Pam Spurr.
Avoid the powder keg
Thankfully, this needn't involve a big sit down conversation under the glare of an FBI spotlight. With a little thought it should be possible to fix the ground rules without reducing what should be a fantastic moment to the romantic equivalent of crafting the Trivial Pursuit rulebook.
After all, what can be better than enjoying a purely physical relationship with your ex, if that's what you're both interested in? Nothing. Not even winning the lottery on the day your team bags a big win over its local rivals.
The key is simply to be cautious and open about the reasons you're getting involved again, as ex-sex is a powder keg full of psychological angst, hurt and recrimination.
Look in the mirror
If you're already involved you need to look in the mirror and ask: am I doing this simply for sex or as a devious ploy to win her heart with some horizontal gymnastics? If it's the latter, then dump your hare-brained scheme in the bin. It will not work.
"Ex-sex is only ever a good thing when both people realise why they're doing it," adds Spurr. "If one is using the other for company and affection, because they're lonely after the break-up, it's likely to backfire spectacularly.
"During the moments they're in bed they'll feel loved, but once it's over and done with and they're back on their own in their flat it can intensify feelings of loneliness and loss."
What could go wrong or right?
So what's the best solution? Well, sometimes ex-sex can provide a useful way for both people to dip their toe back into the relationship waters to see if there's actually anything still there.
At the same time it can allow both sides to share some tender moments and part on good terms with a string of happy memories once the affair runs out of steam. Or, it could result in the dumped person having to go through the whole process of having their heart broken again by the same person.
Alternatively, the dumper could find themselves on the end of a sharply delivered elbow through some twisted form of revenge, while the dumped person uses every ounce of guilt to make their life utter hell.
The truth is that because of your existing baggage the situation is highly volatile, not least because there must have been a good reason that you split up in the first place. So there really is no way of telling for sure.
Is it worth the risk?
One thing is certain: you'll have to do far more than perform in bed to rekindle things fully if that's what you want. At the very least it'll involve expensive dates, presents, the occasional romantic weekend and just about every other shade of couple-based rigmarole you can think of.
So, ultimately, it boils down to the whether you are willing to take the risk, regardless of what you want to get out of it. But then, that same question applies to all affairs of the heart whether ex-sex is involved or not.