He's married, or he has a girlfriend, and you really, really want him? Here's why.

It should be a barrier. You know it should be a barrier. 

He’s married, he’s in a relationship, he has kids, he’s taken. 

But you still want him. Not only want him. You’re convinced you are perfect for him. 

The story of falling for an unavailable man is not new. It’s been told a million times, throughout centuries and across the world. But why does it happen?

There are a few possible reasons. But they’re all down to you.

Is it because it’s forbidden?

There’s the chase. The exciting, all-encompassing, body-tingling, butterfly-inducing chase.

It’s the “you want what you can’t have” syndrome. And neither person being able to act on what they’re feeling adds to the tension and amplifies/romanticises all of it. – Amber, 27.

In these cases his unavailability is part of the lure in the first place. It’s not so much that you believe you’re perfect for him, because you likely wouldn’t like him so much if he wasn’t taken. It’s more to do with the exhilaration, freedom and occupation that comes from wanting someone you are not meant to have.

via GIPHY

This tendency is likely down to your own emotional availability. Maybe the ring on his finger matches the walls you have protecting yourself. That’s why it’s convenient. Because it’s superficial, distracting and also impossible.

“We tend to seek out a relationship that mirrors who we are. If she is going after unavailable men, it is likely because she has some walls built up to protect herself and is not very emotionally available,” human behaviour researcher Dr. Fayr Barkley, Ph.D. told More.com.

You’d be perfect together, you’re just waiting for him to see it.

You love him. You are convinced you know him better than his wife or partner. Maybe he makes you feel that way, maybe it’s all in your head.

Either way, you love him because it’s safe. It’s easy to give all of yourself to someone who you know cannot reciprocate it. You have no expectations and you can live blissfully (longingly) in your head and heart, believing that it would be perfect, that you could be together, there’s only one thing stopping you…

“We want someone we see all the time, who is in our circle but unreachable, who is in our past but untouchable. That seems romantic, and easy to picture,” author and columnist Heather Havrilesky wrote in The Cut. “We know how he would laugh, how he would stare adoringly.Instead of starting from scratch, you’re using a character that’s already fully fleshed-out — like a Ken doll — and placing him in each of your imaginary scenes. That’s not falling in love, though. That’s playing games of make-believe.”

Dangerous, huh?

Again, playing make-believe says more about you than it does about him. Your self-esteem or those same walls won’t let you fall for someone who just might love you back. Because that leaves you too vulnerable. Unfortunately, in the self-torturous cycle that is loving someone who is taken, the situation is likely to feed this insecurity. It’s possible to reach a place where you feel only his commitment to you will make you ‘worthy’ or ‘complete’.

Is it more the idea of him?

I have found myself attracted to people in relationships but I usually quickly figure out that I am attracted to something they represent like success or a happy marriage or a lovely family or a joy for life etc. As I have become happier with my own relationship and family I am less attracted to people in relationships, because I have all of the stuff they have. - Sam, 36.

Again, it's about the things missing from your life that he might be able to give you or he might represent. It's down to you, not him.

Is it that personality?

If he's leading you on, then he's your own worst enemy.

In all likelihood it takes some level of confidence, gravatas, charasima (not to mention utter ass-hole-ness) for a guy who's taken to be leading you on. Whether he's playing the victim-who's-wife-doesn't-love-him or the alpha-I-can-do-what-I-want-male, these traits can come across as infuriatingly attractive.

You might feel you can either 'change' him and be the 'one' to stop his straying ways. Or that you're the one to 'fix' him, when he finally leaves the traumatic relationship he has with his wife. In most cases? Neither are true.

All those words are just words. And you deserve better.

Certainly, it would be helpful if there was an evolutionary switch that turns you off someone who is emotionally unavailable. But, as any one who's ever existed would attest, there is nothing 'helpful' about love. And there's certainly something tragically romantic about being in love with someone who can't love you back. (Even though he secretly does, he just can't.)

But maybe it's more to do with you than it is to do with him. Maybe by addressing your own insecurities, fuelling your own self-confidence (and probably eating lots of Bridget Jones-inspired icecream at the same time) you can switch it off all by yourself. And find the same freedom, safety and a completely different healthy sense of worth in loving someone who is unequivocally ready to love you right back.