The dilemma I have been in an unhappy, loveless marriage for a long time. As a result of this, a couple of years ago I had an affair with a friend’s husband. I had always felt there was a connection between us and after one drunken night we had the courage to explore if there was anything more. He told me he loved me and that I was his soulmate. But he claimed that his marriage was a happy one and that he also loved his wife.

I didn’t enter this relationship with the intention of stealing him, I just wanted to see where it would lead, but I fell harder than I imagined. He told me that I completed him and that he can never get over me. But when I started expecting more from the relationship he ended things.

I know I am in the wrong for having gone down this path, but is he more wrong than me? I would have left my husband for him. I went the extra mile because he kept feeding me lies and I believed them. I don’t know how to get over this betrayal of sorts. I have turned into a shell of a person who has her guard up all the time.

Mariella replies Poor you. First for the unhappy marriage and then the faithless lover. No wonder you’ve got your guard up. You must be on constant red alert for disappointment when it comes to matters of the heart. It has to be said that when you’re asking if a lover is “more wrong than me”, you are excavating minutiae in an environment unlikely to stand up to such forensic scrutiny. But before I get ahead of myself, let’s take a wander backwards, and examine the path you’re presently on and the alternative routes you might have taken.

The situation you find yourself in now, reduced and defensive, can only be tackled by confronting honestly the choices you’ve made. I have enormous sympathy for your sense of betrayal at the hands of an enamoured lover, but having betrayed your friend in order to experiment with her husband, you can’t be so shocked at the existence of deceit. You have the good grace to describe it as a “betrayal of sorts” because to claim any sort of high ground here would be erroneous. He’s betrayed you, you’ve betrayed your buddy… There really isn’t much to choose from between you.

Your affair was not the result of your unhappy marriage but an ill-considered diversionary tactic

There’s nothing more demeaning than to find you’ve fallen for some silver-tongued Casanova who beguiled you into a liaison with promises of eternal devotion, only to find he was just along for the ride. Yet, if we’re being fully honest, you do seem to accept that you were forewarned from the start, just before you go on to denounce this lover for his “lies”.

You can’t bank love or pin your hopes on perpetual desire – neither are stable states. It takes only the addition of the subtlest of elements to entirely alter the form of these impulses. Didn’t his declarations of love sound pretty hollow, even in the moment? As a bystander, they evoke the clichés of any affair: you’re the perfect person at the wrong time; the one who really understands; their soulmate between the sheets; they’re torn between two lovers, and so on.

I agree that even by the standards of passion-fuelled poets he seems to have exceeded acceptable boundaries of credibility. But once he’d made clear the limits of your union and you’d realised you wanted more – what worth were his endearments? Such avowals should be taken with a degree of scepticism, particularly if they’re absolutely what you want to hear.

It’s curious because this man, unusually, seems to have been relatively honest. It’s all too easy to be carried away on a cloud of passion, but much harder to hear what’s really being said between whispered endearments and erotic soliloquies. We are all capable of succumbing to selective hearing, especially when the emotional stakes are at precipitous levels. You seem to have pinned your hopes on rescue when what you really needed to do was make sensible, rational plans for escape.

Your friend’s husband was never your ticket to happiness and he’s unlikely to be hers either if his response to a “happy marriage” is to cheat on his spouse. Your affair was not as you describe “the result of” your unhappy relationship with your own husband but an ill-considered diversionary tactic. You’ve betrayed a buddy and made a poor choice of a lover, both of which I’m afraid are entirely your responsibility. Surely it’s time to let go of whatever declarations were made in the height of the affair and take stock of your marriage instead.

Sitting around stewing over levels of blame is like throwing sticks in the hope they’ll float upriver. I don’t want to moralise, but friendship is precious, sometimes more so than romance, and you should think carefully in future before grasping whatever driftwood floats by, especially when someone else is already clinging to it. You’re in an unhappy place, but at least some of it is of your own making. This man you’re mourning has his bed to lie in – with the greatest respect, I suggest you find a more constructive way of clambering out of yours.

If you have a dilemma, send a brief email to mariella.frostrup@observer.co.uk. Follow her on Twitter @mariellaf1