"I know it sounds like something out of a self-help book, " she explains apologetically. "But it really does work. Research has shown that after a week, happiness improves and lasts for six months, after which time it wanes and the journal has to be done again. It's a way to make you appreciate your life. I suppose people used to pray before they went to sleep, but not everyone does that anymore."

This is the sort of conversation typical of The Health Squad presenter who, although she makes her living from television, is at heart a psychologist. We're sitting at her diningroom table in her old-world, city-centre apartment in Dublin. As she talks she meticulously spreads butter . . . real butter, by the way . . . on warm hot-cross buns, heated especially for my arrival. She serves them with tea and has been to the shop to buy caffeinated tea in case I don't like the decaf she drinks.

Her apartment is warm and inviting; it has big bay windows which let in the dull, February light, there are toys scattered here and there, remnants of Christmas decorations in a box and old-fashioned furniture; it looks lived in.

Having arranged to meet me on her one day off . . . the day when she usually spends 'quality' time with her daughter, meets friends or goes to the gym, she explains that she'll have to fit in the 'quality' time again. It's clear that motherhood is all important to her and it's hardly surprising that it's foremost on her mind at the moment. Keane is heavily pregnant for the second time.

Indeed the most striking thing about the petite 33-yearold is her stomach, and like most mothers-to-be she's glowing. She's six months into the pregnancy and this time round she's having fewer problems. "I found the first time much harder to get used to; second time round I know what to expect."

Although she's a well-known television presenter, the Sutton-born woman has only been working in the medium for the last six years. Before that she was a management consultant, having studied social psychology at college. It's a subject she still gets enthusiastic about, hence the Gratitude Journal and the topic of happiness. "I'm studying positive psychology by myself at the moment with a view to perhaps going back to college, " she offers enthusiastically. "It's just fascinating. It's not pop psychology; it's a way of focusing on people's lives and intervening to make them happier."

Keane knows all about change for the sake of happiness.

She took a chance with her own career six years ago when she gave up her full-time pensionable job to try her hand at television. She was 27 years old and had recently returned from three years of working in San Francisco. "I knew I wanted to work at something different, but I wasn't sure what that was, " she says. "I sat down and did an aptitude test myself. To my surprise acting came out as the profession I'd be most suited to."

She enrolled in an acting course at the Gaiety School of Acting but quickly realised she wasn't really interested in becoming an actress, and decided instead to try television.

"Growing up I had a notion of working in TV, " she says.

"But it was never a realistic option. The realistic option was to study and get a good pensionable job. I thought TV was something other people did; people who came from arty backgrounds or people with connections. It just didn't occur to me that it was something I could do."

When she made the decision to give it a go she saved enough money to last her six months and ditched her fulltime job. "It was incredibly frightening, " she adds. "I began meeting people and asking for advice. I was too embarrassed to admit I wanted to present. Instead I said I wanted to get into production."

One of the people whose advice she sought was television and radio presenter Ray D'Arcy. "He met me for coffee and he was so nice, " she recalls. "But I think he told me I was mad and that I should forget the idea, " she laughs. "I met him at a function years later and I came up to him and said 'remember me?'" Most of the people she encountered were encouraging and it wasn't long until she'd landed a research job on Wanderlust, an internet dating show presented by Brendan Courtney. "I can't say enough about Brendan. He's just a great person. When Wanderlust started he was the next big thing and everyone wanted a piece of him. But he didn't let it go to his head and I admired him for it. That's one of the things I've learnt about being in television, " she adds. "As you get on in life you have to pull someone with you and they in turn do the same. Even if I'm really, really busy I try to make time for other people who need advice because that's how I got my job."

It all sounds very easy but she found it daunting at first.

"I remember my very first presenting job. It was on Wan - derlust and I had to walk along the quays in Dublin with a cameraman and a director. I arrived and the director was dressed in a black suit, he was wearing sunglasses and they both looked so cool. I panicked for a moment and thought, 'Oh my God, I've told these people that I can do this and I actually can't.' Then I took a deep breath and said to myself, 'Look, this is your job. So just do it.'" After Wanderlust she progressed to Open House, where her love of clothes led to her presenting a fashion slot. The Health Squad came next and then last year she was offered the coveted position of presenter with The Afternoon Show alongside Anna Nolan and Blathnaid Ni Chofaigh.

Given the success of the show, it came as a shock to many when she announced last year that she was leaving after just one season. But she had her reasons. "I'd have kept on doing The Afternoon Show if they hadn't extended it to run the whole year, " she explains matter-of-factly. "Originally it was planned to run for seven months and that fitted in with The Health Squad which I film for four months of the year.

As it happens I couldn't do both and I had to choose between the two, " she pauses. "It came down to a decision about where I want to go with my career, my personal needs and the needs of my family. I knew I was planning to have another child and I wondered if I could do it with two children."

Once she took a step back she realised not only had she been under a lot of stress while filming The Afternoon Show but also that she didn't have to continue with it. "The thing about television is that you automatically think if you're offered a job you have to take it, because there are so few of them, but for the first time in my life I realised I didn'tf that this is my life and my goal is not to be famous but to be as happy as I possibly can and to create a happy environment for my family."

Becoming a mother had a profound effect on her thinking. "Having Isobel completely screwed with my head.

Before I used to work very hard and play very hard. Once she was born I slowed down and I realised that if I'd continued as before, I wouldn't have been a decent mum."

She clearly has no regrets about her decision, although of course she misses her colleagues on the show. "People used to assume that there had to be arguments between us but they forget it's not that unusual for three women to get on.

We lived in each other's pockets for a year and the things we know about each other are just not meant to be known, " she giggles.

"It was such an intense environment and it felt like there was magnifying glass on the three of us; that created a bond and made us good friends. What's more, we all had different personalities and interests so there was no competition."

It's hard to imagine anyone not getting on with the bubbly presenter, but does she ever get depressed? "I only get down if something really major happens to knock my confidence, " she confides. "Usually I'm quite a positive person.

I'm totally delusional, " she laughs. "If I go for a job interview for example and I don't get it, then I come away thinking that it wasn't the right job for me, rather than thinking I'm crap."

One person whose positive attitude she admires is her husband Jonathan Forrest, owner of a digital media company.

The couple were childhood sweethearts who met in UCD at the age of 18. "Jonathan is incredible, " she enthuses. "He has boundless energy and he puts so much effort into relationships with people. He's a very happy person and he's automatically appreciative." She smiles. "I'm aiming to be like him."

With her matter-of-fact approach to life it's easy to see why she's good at dealing with change and helping others to improve their lives. I get the feeling that she'd be quite good at anything she put her analytical mind to. She's the kind of person who you feel could sit you down over a cup of tea and explain to you exactly where you're going wrong. In fact I want her to sort my life out right nowf And this is what interests her. "I've realised you have to work at being happy and having a good life. I'm interested in making good, positive TV; programmes that help people get out of the rut of everyday living; that's what I enjoy, " she says, adding that she loves working on The Health Squad.

But is she particularly healthy I wonder? "I'm a relatively healthy person, " she says. "I try to eat healthy food. For example, I don't eat anything from a packet. I cook everything from fresh and I buy organic as much as possible. I eat plenty of fruit and vegetables." And what about exercise?

"I hate the gym, " she screws up her face. "I swim instead and I do a lot of walking."

Keane hopes to continue presenting and producing in the future. She had a hand in producing the most recent series of The Heath Squad for the first time this year. "Perhaps eventually I'll go behind the scenes full time, " she muses. "After all it's where I started in the first placef But I don't worry about the future, " she adds. "What's the point? I've been lucky so far; let's hope that continues."

Sheana Keane presents 'The Health Squad' on RTE One Thursdays 8.30pm