The dilemma I’m 50 soon. I’m happily married, I have friends and my work is fulfilling – but I’m desperate. My mother has Avoidant Personality Disorder. She’s getting therapy, which she says won’t work. She never remarried or had a relationship since I was a baby, and she has no friends. Over the past few years, my husband and I have taken her on holiday. Now she keeps hinting that my husband “needs a holiday” – I know exactly what she means. I don’t know how to tell her that we need time to ourselves. She looks for chinks in my armour and is delighted when I’m wrong. I’m exhausted by her bullying, catastrophising and ridiculous silent treatment. I can stand up to her, but she denies her bad behaviour. She hit me once – she knew she’d gone too far and could see I was angry. She uses her illnesses, jealousy and loneliness as a lever against us. I’m forever treading on eggshells. I want a holiday, with my husband, alone, but it feels like I’m asking for too much. I feel like a crap daughter.

Mariella replies You’re certainly not. Though if you stopped accepting your mother’s load as though it were your own you might be an even better one. Supporting her struggle to lead a normal life is the decent thing to do, enabling her not to have to confront her peccadilloes is altogether different. There is a natural evolution in the relationship between parent and child that culminates in the end of dependence, but hopefully not of love and mutual care. It’s a clear line that needs to be respected on both sides of the generational divide and my sense here is that her situation has engulfed you in a tangled jungle of compassion, responsibility and guilt.

As a mother of teenage children I had, until recently, imagined I’d always have them in my grasp, but it’s increasingly clear that my tenure as supreme being has run its course and my reign is in decline. My kids embrace news that I have to be away on work not with sorrowful faces but euphoria and celebration. Soon they’ll be booking flights to the four corners of the earth to escape me with not so much as a backward glance. It will be painful, lonely and bloody annoying having invested so much in my beloved but now over-sized and occasionally sullen babies. But leave they must. The natural order has to be preserved and it’s increasingly obvious that it’s my children’s turn to run the world and raise the next generation while I put my feet up.

You can neither cure her nor protect her from her demons

I’m pointing all that out because your mum has seemingly forgotten who the child is in your relationship. I’m really sympathetic to her debilitating condition, but relieved to see you have managed to establish a healthier, more fulfilling approach to your own life. There’s a clinical definition and diagnosis for almost every human dysfunction these days, and we’re making great leaps in our understanding of why people act as they do and what can be done to limit the damage before we pass it down. But the broad-brush stroke approach to medicalising conditions, while leaving no room for nuance and degree, can also be responsible for inspiring a sense of futility, particularly in vulnerable individuals, that too easily slips into defeatism or an abdication of personal responsibility.

You are clearly a diligent daughter who has gone out of her way to enable your parent to more positively navigate the parts of life she finds tricky. Having her best interests at heart, along with offering her emotional support and practical help, are to be applauded, but turning your marriage into a co-dependent threesome is taking things to an altogether less healthy level. Permitting her to express her frustration in physical violence towards you should be an absolute red line.

It does sound as though you have taken too much of the burden of your mother’s condition on your own shoulders. You don’t mention siblings, but social services have a duty of care, including to offer respite to carers (rethink.org). Is there reluctance on your part to involve others in what you see as your problem? If so, despite the cliché, remember that a problem shared is at least partway to being a problem solved. Despite her avoidant personality disorder your mother is accountable for her actions and you can neither cure her, nor protect her from her demons.

It’s because of the amount of time you’ve invested in your parent that I suggest it’s compulsory that you and your spouse go away and spend quality time together. If you allow your relationship to be hijacked by her demands then, eventually, you’ll find the only relationship you have left is with your mother.

When it comes to entering adulthood it’s pure instinct that propels us out of our parents’ door – a severing of the umbilical cord so we can embrace our own destinies. For parents, it’s equally important to let go with dignity and not rely on our children to keep us aloft.

You are your mother’s daughter and you have lived up to your side of that expectation by supporting her . Now it’s time for you to embrace your own existence with an equally strong sense of duty.

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

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