Q. We've been married for 15 years and have three children aged six, eight and 12. My husband is a good person and he has always been faithful, yet I find our marriage gets more and more difficult. He has always been moody, and though he has a good career, he never seems to be satisfied and his work dramas often create an atmosphere at home. We rarely have sex, as I never feel like it. We seem to bicker all the time, and although I do love him, occasionally I think I hate him as well.

Sometimes it just seems as though life would be so much easier without him. I feel exhausted by our relationship and the feeling that I constantly put more in than I really get out. Outwardly, our lifestyle is great and people envy us. But I don't know how to face years more of this. I look around at the couples I know and I can't help wondering: how do people keep long marriages going?

A. Like you, I often ponder the mysteries of other people's marriages. Sometimes I wish it was OK simply to ask them how it all works ("So, have you really forgiven his affairs or do you stay with him because you can't bear to give up the house?"). But having seen lots of people's marriages come and go, I've come to the conclusion that what keeps people together, sometimes through infidelity, decade-long sex droughts, bickering, boredom, alcoholism or intense irritation, is simply that both of them want the marriage to last. Often this is because, despite it all, they really love each other. Sometimes it's because the alternative is too awful to contemplate.

Someone once told me that women with a perfectionist streak are more likely to stay in an abusive relationship as they find it difficult to face up to failure (perhaps also because highly ambitious people have a tendency towards self-loathing). Maybe perfectionists are more likely to stay in any marriage: marriage breakdown and single parenthood mean one fewer tick in the "success" box.

As a single parent, I've had a fair bit on my plate over the years. Things I don't or haven't had: money; spontaneous visits to the pub; a social life; career advancement; an adult to enjoy doing nothing with. But I also don't have the huge job of managing a relationship or negotiating someone else's moods.

Marriages don't run themselves, and any marriage involving three children and two (I'm guessing) careers has dark forces working against it. It's shocking to feel hatred towards a loved one, but actually these powerful emotions go hand-in-hand. You love your husband and it sounds as though he loves you. Why would you not stay married?

You need to agree between you to apply the same level of nurturing and effort to your ailing relationship as you do to your children and your work. Effort sounds unromantic, but it's necessary. His moods and your sex drive (perhaps related) should be top of the agenda. Neglect the children if necessary and devote a year to this. There's so much to lose, and to gain. Don't watch it fester – do something.

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