Want happiness? These 2 simple but not always easy approaches almost guarantee it.

Many millions of words have been written on how to be happy, which is both a blessing and a curse. If you’re an entrepreneur in the market for tips, there certainly is no shortage of suggestions from everyone from scientists to billionaires to Albert Einstein. But who has time to wade through thousands of articles? And which of the many ideas out there should you try first?

What you need to get started is condensed and easily applicable advice from someone who knows what they’re talking about. A quote from British philosopher Bertrand Russell fills the bill, and better yet, his suggestion is backed by modern research.

The secret of happiness in just 35 words?

Russell was a celebrated mathematician and philosopher who died back in 1970 at the age of nearly 100. He’s the source of many popular quotes, which writer Thomas Oppong recently rounded up on Medium. If you’re looking for a reminder of the downsides of materialism, the value of intellectual humility, or the high chance worrying what others think of you will lead to regret, then it’s well worth a quick read.

But one quote from Russell’s 1930 book The Conquest of Happiness struck me in particular as packing a whole lot of profundity into just 35 words: “The secret of happiness is this: Let your interest be as wide as possible and let your reactions to the things and persons who interest you be as far as possible friendly rather than hostile.”

As Russell explains in the book, the world is huge and we are small. You’ll never have enough time for everything you want to do in your limited years. That truth could bring despair if you constantly fight against it. Instead of struggling, he advises you pick interests that captivate you (his very personal examples are “the Council of Trent, or the life history of stars,” but football or knitting would do just as well) and get lost in exploring them. This way you can temporarily slip the constraints of time and find momentary happiness.

In short, practice openness and get some hobbies or interests. Then use them to find flow. It’s a simple enough prescription, but it’s actually one that’s backed by modern science.

Modern research agrees

Openness has been linked by research not only to creativity and intelligence, but also to slower mental aging. Being open to new experiences seems to help keep the mind young. So, science certainly has found benefits to being friendly rather than hostile to new people, interests, and ideas. And should that initial curiosity develop into a hobby or interest of some sort, so much the better.

A stack of studies shows that having diverse interests helps us develop a broader sense of self. You’re not just an entrepreneur and a dad, for instance, you’re also a bowling league champion, a surfer, or a sourdough master. Which means that whenever we run into difficulties in one of these areas of life, we can draw strength and confidence from others. When business is rocky, the surfing waves might be rocking.

Not only are hobbies and interests a resilience booster and a stress killer, they also help us enter a state of flow. This is that feeling you get when you’re doing something you genuinely enjoy and lose all sense of time. Psychologists have identified flow as a sure route to happiness — when you’re deeply absorbed in an activity, you are not fretting about the future or the past.