A FRIEND called recently, asking me to rank my personal happiness on a scale of one to 10. I sighed or squirmed; probably both. It seemed a particularly moronic way to measure something so important. Still, the good friend lives on the other side of the world and seemed to be having a tough old time of it, so I paused briefly to calculate my overall level of happiness.

"Six."

"Me too," he said. "A six seems about right most of the time."

"A six isn't bad," I suggested.

"It's not bad, but it's not very good either. Imagine being a seven most of the time. Or an eight or a nine. Wouldn't that be great?"

January, at least on this side of the world, is not typically the time of year to think about reaching eights and nines. According to Cardiff University research, tomorrow is the most depressing day of the year. I usually find every one of January's 31 days thoroughly miserable. It's tricky enough avoiding the flu, ignoring a faltering bank balance, and readjusting expectations as Liverpool FC and the title race once again go their separate ways. Then there's the weather.

And yet, there was something compelling about that good friend's enquiry. It had forced me into a corner, leaving no room for self-deception about my typical state of mind, whatever the season. Also, it made a pretty decent level of happiness seem tantalisingly close.

So it was only mildly surprising to learn that the one-to-10 scale is commonly used by leading psychologists attempting to decipher individual wellbeing, even their own. American academic Martin Seligman, who first set out a manifesto for the scientific study of happiness 10 years ago, says he rates his happiness this way once a year.

It was Seligman who launched the positive psychology movement with a speech to the American Psychological Association in 1998. He told the audience their profession had become obsessed with depression and neurosis. If instead they focused on happy, well-lived lives, they might discover the key to helping everyone become more content. As a rational, critical thinker (that's one of my signature strengths, according to Seligman's online questionnaire), I find the self-help profession's insistence on leaving the light of optimism permanently switched on a little draining. But when Tal Ben-Shahar, Seligman's protégé and a luminary of the positive psychology fraternity, agrees to meet me in Glasgow, it seems an ideal opportunity to work out if becoming a seven-out-of-10 sort of person is at all realistic.

With perfectly standard adrenaline levels and an average number of teeth, Ben-Shahar does not come across as the archetypal new-you life coach. He began teaching a course on happiness at Harvard in 2002 to just eight students, but word about the class's feel-good benefits quickly spread. The following term, over 300 turned up. The year after there were 900 undergraduates seeking instruction, making Ben-Shahar the most popular lecturer in the university's history.

The Israeli psychologist tells me that his own quest for happiness has been difficult, and admits it led him to the bookstore self-help section. "As an undergraduate I was doing very well academically, socially and in sport, but I wasn't happy," he recalls. "It just didn't make sense to me, because externally things were going so well. I did start thinking maybe there was something inherently wrong with me.

"I began reading a lot of the pop psychology and self-help literature. Although I enjoyed some of the books, many of them overpromised and underdelivered. Not only did I not find the five steps to happiness, I became increasingly frustrated, because the prescriptions didn't work. But of course, there are no five steps. I don't believe there is any simple secret to success and wellbeing."

At the core of Ben-Shahar's own brand of positive psychology is an invitation to discover and cherish the things that gives us meaningful pleasure, rather than consistently indulging in short-term gratification or escapism. We should find more time to appreciate activities and people that grant the kind of happiness that lasts.

So far, so sensible, I thought. Only in the last year or two have I gained some insight into what these meaningful pleasures might be. Various kinds of writing have brought real satisfaction. It has also become easier to cement the friendships which really matter. So why has it taken so long to get some inkling about what really makes me happy?

"There are many prevailing pressures in our culture about what constitutes happiness," says my temporary teacher. "We think if we get enough promotion, prestige or accolades then we will happy. External, material attainment is so much part of our ethos. But it's short-lived and very quickly we go back to where we were before, emotionally."

A few chapters into Ben-Shahar's book, Happier, it is easy to identify myself as one of his "rat-racers", forever living in the hope of some future happiness. The psychologist recommends that I write out prime sources of pleasure each day, an exercise in gratitude his students have found helpful in living for the present.

Ignoring my internal cringe-o-meter, I jot down second-hand bookshops, Ealing comedies, table tennis and green tea: a list that makes my life feel a little inconsequential. Ben-Shahar insists the method works, for himself as well as for others.

Some of the online positive psychology tests prove more uplifting. After answering several questions with modestly positive answers such as "somewhat more often than not, I get what I want", I score 2.93 out of five in the overall happiness stakes. In a glass-half-full mood, I round it up to a three. If my happiness were a film, it'd be a mid-1980s Woody Allen comedy. Radio Days perhaps, or Broadway Danny Rose. But serotonin levels dip again when I realise I have ticked the box marked: "My existence neither helps nor hurts the world." A grim predicament. Friends have often told me that voluntary work makes them feel much better about themselves, but this has always seemed too selfish a motivation for apparently altruistic activities.

According to Ben-Shahar, I have failed to see the bigger picture. "Research shows regular acts of kindness, benevolence and volunteering can add significantly to our sense of well-being. Happiness creates inter-connectedness. It's not just an individualistic thing. Happiness is socially beneficial."

Am I being too self-centred, too greedy about happiness? I confess to Ben-Shahar that I'm feeling envious towards those abnormally cheery souls that appear to glide through life unscathed, hogging more than their fair share of bliss.

"Well, jealousy is a natural emotion," he chuckles. "It's true that there are people with really positive dispositions, and some of that is determined genetically. But there is no-one out there experiencing a constant high of happiness. In fact, quite often the people who seem to us the happiest are the ones who have experienced difficulties and hardship. They've learned to cope and have become more appreciative of what is good in their lives."

Some subdued, part of my brain has known this all along, but required intelligent exposition from a fellow rationalist. "I wasn't born with a positive disposition either," confides Ben-Shahar. "I wasn't born with a smiley face. I've had to work at happiness and I still have to work on it. The wonderful thing is that it's possible to work on it and become happier throughout life."

Happiness is hard work. Odd that this should feel so reassuring. The next time my good friend calls late at night, I might actually have a few words of wisdom to pass on.