People are often genuinely shocked and heartbroken to discover that their spouse has been unfaithful.
But in many cases, there were a number of key signs there all along that they simply failed to spot.
Here, relationship expert and Perth's Millionaire Matchmaker, Louanne Ward, has spoken to FEMAIL about the signs to look for and the different kinds of cheaters you may come across.
'There are several different types of cheaters and infidelity comes in different ways, shapes and forms. The most common of these I've narrowed to three types of cheaters and the tell-tale signs can vary slightly,' Louanne said.
'Are they a once off cheater? Are they a thrill of the chase, repeat offender? Or perhaps they are an accidental cheater.'
THE ACCIDENTAL CHEATER
Ms Ward said most people feel for this kind of cheater as 'they have convinced themselves and anyone else that knows that this is a very tough situation'.
They will be going through the 'we didn't set out to hurt anyone' and the 'I love my partner but I'm not sure if I am still in love with them lines'.
So what do you need to look out for?
'They will start by talking about a new person at work, at golf or tennis club etc. and you won't think too much about it until it starts to almost become awkward,' Louanne explained.
'At this stage of the connection you can be confident nothing has happened. People who are guilty don't talk about the crime.
'As the attraction grows suddenly, your partner stops talking about the random stranger who has crept their way into just about every conversation for the past few months. Then like magic, poof, they disappear and there is no mention of this mystery person.'
You may notice that this person is starting to stay back at work a lot, starts having lots more events to attend (using their boss or friends as an excuse), is travelling more and is being noticeably more expressive and happy with their body language while on the phone.
This person will likely also amp up their social media use and become suspicious about it, close apps and pages down when you walk in and start saying things like 'I'm not happy' or 'I just need some time alone'.
Other signs include less frequent sex and affection, not kissing you like they used to, coming home late from work and having a shower before bed.
'This is not uncommon, however after being 'out with the boys or girls', if they mysteriously shower before offering you any affection it spells alarm bells,' Louanne said.
'Often they will also start spending more time with the kids, because they begin to feel guilty due to the possible upcoming breakup of the family. Therefore, they start trying to improve their relationship with the children as a result,' Louanne said.
THE ONCE OFF CHEATER
'This type of cheater is a once off cheater. They may just have a momentary lapse of judgement during an innocent break from the routine like a boy's/girl's trip, weekend away or business trip,' Louanne said.
Signs of this cheater include them becoming standoffish and uncharacteristically uncommunicative or going out of their way to tell you how much they love you.
'They will tell you they love you but the lip service doesn't turn into the full after sales service,' Louanne said.
These people will also likely have moments of guilt and buy you unexpected gifts or seem more distant when spending time with you even if you are spending more time than usual together.
'Often, they will make plans to go somewhere nice but when you get there the conversation is stifled,' Louanne said.
'You ask what's wrong and they say "nothing, I've never been happier".
They will also likely daydream a lot and put any distant behaviour down to being 'stressed at work'.
THE SERIAL CHEATER
'If a cheater gets away with cheating, the thrill of this can become exciting. Which is why, "once off cheaters" often become serial offenders. So, it's very important to look for the telltale signs,' Louanne said.
'This type of cheater is a repeat offender and will continue to cheat again and again as they love the thrill of it.
'Getting away with the crime gives them the power fix they desire as typically they have a narcissistic personality.'
So what should you look out for?
'This narcissistic cheater is a seasoned pro so they can be harder to detect because they have mastered their craft,' Louanne said.
'Often when you first meet them and ask what happened in their last relationship, they will tell you that their ex was insecure and jealous and after a while it affected their relationship.
'They will go out of their way to tell you they have friends of the opposite sex and if you are going to have a problem with that it's not point continuing as they don't want to live the nightmare again.'
After laying this base down, this cheater now has their 'get out of jail' card if they need to use it, Louanne explains.
'We cannot conclude they set out to commit the crime again, in fact many of them think "hey I really like this girl/guy they are different, I'm going to try and make it work". But what happens when reality sets in and the addiction raises its ugly head? What are you up against?'
Louanne said this cheater is the hardest to identify as they 'know the track and have the road map imprinted in their dialogue'.
Although the same rules apply as the other types of cheaters, there are a few extra things to look out for.
'When you raise the normal questions about where they have been, whether they had a good night and who were they with, what you don't expect in return is their defensiveness,' Louanne said.
'They'll say things like 'why are you asking me, you are making me feel like I've done something wrong' or 'why are you being suddenly insecure? I'm not going to talk about it'.
'You almost feel guilty as if you have wrongly accused them. However, as the weeks and months go on and more signs emerge you find yourself on eggshells.
'In your heart you know something is not right but the cunning serial offender almost has you believing it's all in your head, in fact they will confess their undying love and in the same breath suggest you get help as you are ruining the relationship with your insecurities.'
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