When my eldest son was eight he earnestly asked what flowers I would like on my grave when I was dead. He was doing a project at school on smoking and health and clearly saw my days were numbered. The incident upset me terribly and I gave up cigarettes that week.

I had been a heavy smoker, starting at about age 14, and smoking guiltily through two pregnancies. The year I gave them up stands out as the most miserable time of my life. I chewed gum and took up new hobbies but it was a long time before I felt nicotine-free and even now - 12 years later - I sometimes hanker after a cigarette.

But my life certainly changed for the better. I became fitter, had more money and people have told me I look and smell better than when I smoked.

I now have three children, aged between 12 and 20 - and all three smoke.

The younger two do it clandestinely, but the oldest has "come out", which means he smokes in front of me. I made a rule against smoking in the house, but when I return home unexpectedly there is always a decided whiff in the air. We battle constantly over this, but he can always silence me with the simple statement that I passed on the addiction because I smoked when I was expecting him.

The whole issue of smoking is fraught with emotion in our household. So imagine my delight when he announced on Ash Wednesday that he was giving them up. The information he had collected while doing the project 15 years ago was at last relevant to him.

We are now at day 20 and I have to keep reminding myself of the misery I went through all those years ago. His behaviour is appalling. He is bullying the younger two because they are still smoking and, while I admire the objective, his tactics are questionable: yesterday I found him holding his sister in a vise grip while he demanded to know where she was buying her cigarettes - he intended to report the vendor to the Garda.

And his mood swings: one minute he is hyperactive, running around with an energy level that exhausts me, and the next he is languid and lethargic. His appetite has trebled and he is munching chocolate one minute and chips the next. His sleep pattern seems to have gone. He has taken to watching TV at 4 a.m. and then nods off in mid-conversation.

He is really going through hell, and of course I have to support him all the way. Now he tells me he has persuaded the younger two to join him.

The fragility of my mental health is quite evident. Maybe I could sue the tobacco companies for bringing on premature dementia?