Is having the perfect job, family and being in love the key to a happy life?
Researchers, philosophers, spiritualists and others have spent years seeking the answer. In recent times, even the UN has measured people's happiness.
And tomorrow we will find out how happy we are compared to the rest of the world. The latest World Happiness Report will be released to coincide with International Day of Happiness. Published by the UN's Sustainable Development Solutions Network, it ranks 156 countries by their happiness levels.
Last year New Zealand ranked at No 8 - one above the Aussies but not as merry as the Scandinavians. Denmark came out on top, the US was 13th and the poor old UK didn't even make the top 20.
Burundi was the most miserable on the planet, followed by war-ravaged Syria, Togo, Afghanistan and six other countries in sub-Saharan Africa.
But what is happiness? To some it is a human right. Alongside the rights to life and liberty, crafters of the US Declaration of Independence added the pursuit of happiness.
And the town of Madison, New Jersey, will tomorrow set a precedent as the first US town to celebrate the United Nations' global holiday. The town will be painted yellow for the day, through art exhibits, fundraisers and people dressing in yellow.
And in the UK, last week it was revealed 8-year-olds are to be given happiness lessons and teenagers instructed on combating anxiety and suicidal thoughts, in Government projects due to be trialled.
The Department of Education is inviting bidders for multimillion-pound contracts to offer mental health training in more than 200 British schools.
Typical mindfulness lessons will reportedly encourage children to think of disturbing thoughts as "buses" that will move away, and they will be given questionnaires on bullying and friends.
Happiness means different things to different people. Many view personal happiness as simply a state of well-being or a pleasurable or satisfying experience defined by positive or pleasant emotions.
But philosophers and religious thinkers often define it in terms of living a good life, or flourishing, not just as an emotion. And, they say, it is something money can't buy.
Professor Marc Wilson, at Wellington's Victoria University, argues about 50 per cent of happiness is genetic.
"Research shows if your parents are miserable, you are likely to be miserable too," he says.
"Similarly, if your parents are chirpy, you are likely to inherit this attitude.
"At the same time, about 10 per cent of happiness is down to what is going on in your life and the other 40 per cent is related to how optimistic or pessimistic a person you are - how you choose to react to what is happening daily.
"In general, most people seem to have a baseline for happiness. It doesn't matter if you are dealing with a death in the family or have won the Lotto, eventually we return to that baseline of contentment."
"When I was young(ish) happiness was all about laughing with friends and partying until the night has no hours left and the alarm clock is going off in a bedroom you haven't seen all weekend. As I moved through my 30s happiness has become much more calm. My children give me a busy happiness that encompasses all other emotions at the same time.
My wife gives me a happy excitement that puts a smile on my face when I see or think about her. To me, happiness is not an epic emotion that burns like fire, it is a steady calm emotion that can be with you always. I chose a job where laughter is 80 per cent of my
work life. Laughing is one of the gates to find happiness and if you are laughing while you
work, then the gate is usually open."
Dame Valerie Adams
"Making people laugh. I love having fun and having a bit of a laugh. I'm serious in training but also know it's really important to stop and have laugh or bit of banter. Sharing special moments with your loved ones makes me happy. I've had some pretty special times but I get real joy in sharing those times with those who are close to me. Great food also makes me happy but sharing it with my husband is even better.
I love baking for fun and for others, so doing some baking and then sitting down and sharing it with hubby and friends is awesome. And of course, setting goals for the year and then working hard to chase them - that makes me happy."
"Life makes me happy because every day is full of opportunity and the chance to do better. And to do something different, and to achieve and improve."
"Spending quality time with family and friends and putting a smile on other people's faces is what makes me the happiest. I like being alone and connecting with nature - beach and bush walks are always a happy time, but like many others I'm sure certain music, sports (when the team is a winner) and the gym also to take me to a happy place."
"Make the most of little things. The first sip of coffee every morning, the first bite of breakfast and a good game of backyard cricket. And icecream!"
"For me happiness is all about those moments when you're in the zone, when everything is falling into place and you're firing smoothly on all cylinders.
It's a bit like the perfect tee shot when the club hits the ball in the sweet spot and it soars along the fairway and rolls onto the green. Happiness is also about those moments at home when I'm most relaxed, like those summer evenings, in the backyard with my family, a beer or wine in hand and you're winding down listening to music, enjoying the moment."
"Well, what sort of happiness are we talking about? Beer makes me happy, and fried chicken, and girls in bikinis, and cigars, and putting money on horses. But it's not the right sort of happiness. All of these just make you want more of the same thing, like a mosquito bite that gets itchier the more you scratch.
The other, better, more lasting sort of happiness is the feeling I get when I walk through native bush, read a book, hang out with my children or pat a friendly dog. Science shows this sort of pleasure is chemically different to the other. Life in 2017 is trying to get through a New Yorker article without clicking on photos of Reese Witherspoon without makeup."
"What makes me happy is spending time with family and friends - especially quality time with my daughter. Good food and wine always takes me to my happy place. If it's at a beach or the waterfront - even happier!"
"Being a parent is the hardest thing I've ever done but also the most rewarding. My kids make my heart sing and enrich every experience. I love adventure. I used to host a travel show and it was pure joy having my eyes opened to new cultures and ways of life. And cake! I associate it with happy celebrations. I love cake so much."
"I don't think I'm going to know happiness until I'm holding my first grandchild in my arms. I think then I will truly know real happiness."
"It was a whole new experience when I had kids. It was a level of happiness I didn't know existed."
"That famous philosopher of the 1980s, Ferris Bueller, said: 'Life moves pretty fast. If you don't stop and look around once in a while, you could miss it.' I've always told my children that in every day there are small moments of great joy, but you have to stop and notice them. Reaching the top of Mauao (Mt Maunganui) is one of the things that makes me happy.
It never seems to get any easier and halfway up I always enter into a debate with myself about the wisdom of the whole journey, but that view from the top makes every aching muscle worthwhile."