In 1799, German poet Heinrich von Kleist conveyed to his sister that happiness, unlike a mathematical theorem, cannot be proven. Instead, he emphasized that it must be experienced to truly exist. However, over the past decades, researchers have tried to do just that, looking at what it means to feel happy and what can help us to achieve that state.

According to Dorothee Salchow, the joy derived from luck, like winning the lottery, doesn’t make us happy in the long run.

Instead, she likens happiness to a state of "well-being, the inner experience of human happiness."

Salchow, a life coach trained in positive psychology, knows what leads to sustained happiness. And she has the science to prove it.

Introducing positive emotions

"According to everything we know from research, positive emotions have a strong impact on our well-being," says Salchow.

"That may sound counter-intuitive at first, to look for positive emotions when you’re not feeling well. Basically, it is important that all emotions or feelings are allowed to exist."

If you want to increase your well-being, it’s worth reflecting on your day and taking stock of the things that sparked your interest, that made you feel amused, happy, proud or loved, Salchow recommends.

As a blueprint, the psychologist recommends "the big 10 emotions" studied by positive psychology scholar Barbara Fredrickson: Love, joy, gratitude, serenity, interest, hope, pride, amusement, inspiration and awe.

"We know that experiencing positive emotions leads to us being able to perceive and process more stimuli in the short term," Salchow says.

Experiencing positive emotions increases the formation of neural connections, she explains, which supports our mental flexibility and creativity, as well as our problem-solving ability.

"As a result, we build up new resources that we can access in the short term, and in the long term this leads to us being able to cope better with our everyday lives and experience more positive emotions."

Knowing, using your strengths

Another way to boost your happiness is to reflect on your own strengths, the coach says.

Instead of looking at specific skills, like being good at math, try and think about how you go about things, Salchow recommends. For example, you might find that you are a very prudent person, or have a great sense of beauty.

Knowing our strengths and utilizing them helps to improve our well-being in the long run, the expert says.

Other well-researched positive character traits include curiosity, judgment, fairness, wisdom, social intelligence or even humility, according to Salchow.

Having sense of purpose

If you want to be happier, it always helps if you are doing something that feels meaningful, the coach says.

"Studies have shown that people with a high sense of purpose are happier," Salchow says. Whether at home, at work or when doing volunteer work, try and find something that allows you to contribute to the bigger picture, she recommends.

Setting, achieving goals

For many people, the to-do list might be the ultimate downer, but "setting and achieving goals also makes us happy," according to Salchow.

When setting yourself goals, it doesn’t always have to be extraordinary things like running a marathon or getting a degree, the expert says.

"There are times in our lives where making it out the door once a day is already an achievement.

"It is important for our sense of happiness that we recognize this as a goal and as an achievement – to pause, so to speak, and say: Look, I’ve done it!"

Healthy relationships

"The absolute number one factor for more happiness in life are good, supportive social relationships," Salchow says.

Since 1938, Harvard University has been running a Study of Adult Development, one of the world’s longest, looking at psychological variables and biological processes in two groups of men over the past 80 plus years, to understand their impact on health and well-being late in life.

This study has shown that happiness doesn’t depend on having lots of relationships, Salchow points out. "It is enough to have one or two people in our lives whom we perceive as supportive."

It’s also been found that doing something for others or supporting someone else’s happiness makes us happier than trying to make ourselves happy, she adds.

That means it’s up to us to turn a relationship into a supportive one, which at the same time will also contribute to our own happiness, Salchow says.

What stands in way of happiness?

Robert Waldinger, director of the Harvard study, has written a book about it called "The Good Life – and How to Live It: Lessons from the World’s Longest Scientific Study of Happiness."

In it, he divides happiness into two categories: One is a hedonic sense of well-being, which means "I am having a good time right now."

Then there is eudaimonic well-being, "the feeling that one’s life is meaningful and fundamentally good."

While with hedonistic well-being it is clear that we are enjoying ourselves in that moment, this is not necessarily the case with eudaimonic well-being. For example, reading the same bedtime story to your child for the umpteenth time is often not fun. "But is it the most meaningful thing you can do at that moment? Yes," Waldinger argues.

There’s often a difference between what brings us immediate joy and what feels valuable or meaningful.

Every person needs to experience both, according to Waldinger.

We start running into problems when we only chase after hedonistic well-being instead of "the more mundane, but ultimately more meaningful kind," the happiness expert says.