'I'll never forget my first run... I chose to run on a public road. That way I figured I'd be too embarrassed to stop' Roisin Carabine

Training and fitness aside (we'll get to that later), deciding that you're actually going to run a marathon is the easy bit. Telling other people of your intentions isn't quite so straightforward.

I wasn't expecting the different reactions I got. Work colleagues and friends were impressed, even encouraging. The same could not be said for my family however. They thought it was just another crazy idea in a long list of crazy ideas of mine.

My mum was worried about my heart. My knees. My running on the roads. My running at night. My running in the morning. My eating. My not eating.

My dad was worried I'd become addicted to running, seriously – like heroine or cocaine. This was a bad thing. Even my husband was sceptical, although he did manage to feign an encouraging smile and would pat me on the back every time I put on my shorts and trainers.

I've always wanted to run a marathon. I just never thought I'd get around to doing it.

I used to run in my teens, competitively too, but at 34 I've now more experience not running than running.

For the last number of years I can safely say that I've engaged in no physical activity whatsoever other than my yearly trips snowboarding, and that's only for one week. Oh, and running (breathless) to the bus stop in the mornings.

My decision to run this year's Dublin marathon was spurred by my friend having run the Belfast marathon in May, and at a very respectable time of just over four hours. She was as unfit as me.

The secret to her success, aside from pounding the pavements and eating piles of pasta, was a book,
The Non-Runner's Marathon Trainer by David Whitsett and Forrest
Dolgener. It's become my bible.

The book is based on a marathon class offered by the University of Northern Iowa and is specifically aimed at first-time marathoners with no running background whatsoever. It's "marathon running for real people; people with jobs and families and obligations outside of running". People like me.

The marathon training is done over 16 weeks (just four months), running four times a week (which you have to do; running a marathon is not like studying for an exam – you can't cram it all in at the last minute), with the longest run on a Saturday or Sunday.

I started my training back in July. I'll never forget my first week, or my first run. It was three miles of pure torture. I chose to run on a very busy, public road. That way I figured I would be too embarrassed to stop. I didn't stop but I panted my way around the route like a dog on a hot day, with my head flopping about from side to side and my tongue hanging out.

By week six I was running 11 miles on my longest run, averaging 26 miles a week.

The training does actually work. It's about shocking your body into running and increasing the mileage every week so you don't get used to the same runs.

The upside is that I'm fitter now than I've ever been in my life. I've even managed to lower my cholesterol. The downside is that running a marathon is just plain boring. The first three miles for me are still always the hardest. I have to constantly remind myself not to give up. The temptation to stop is just so appealing, especially when it's raining, or cold, or windy, or because running such long distances just seems so pointless. It's not fun; the only fun part is when you get to the end.

The last couple of weeks I've tried listening to music. It hasn't made me run any faster, even when I switched to hard rock, but it has taken my mind off the running.

The book doesn't recommend listening to music. It advocates listening to your breathing, focusing on the positive and using mind-over-matter techniques like going through the alphabet and thinking of names beginning with each letter. On my longest 18-mile run I ran the whole route counting to 100 over and over again. It actually worked. I felt totally elated and even managed a pretty good time.

Aside from the actual physical training (I've had shin splints, tendonitis, swollen knees and plantar facilties), the hardest part has been running on my own. I've had no-one to encourage me along the way when I start to flag or to pace myself against. I've had to rely on willpower and a stopwatch.

If I'm honest, I'll admit that my real motive for running the marathon was to lose weight. The book, though, quickly dispelled that goal by about chapter two. Running a marathon is not a weight-loss class and by attaching inappropriate expectations to it you could lose out on what can be one of the best experiences of your life.

As a consequence of the training I have lost weight, just over a stone. And bizarrely through eating. I've been packing in the carbs and stocking up on water and energy drinks. All the training in the world amounts to nothing if you don't eat or aren't properly hydrated, as I found out several times.

Tomorrow I put all my training into practice. I am nervous. I'd love to run the 26.2 miles in four hours, but finishing it without stopping will be just as good. I'm even seriously considering signing up for the Belfast marathon next year. Turn's out my dad was right – running is addictive.