This free and easy hack can help you be happier — it’s not exercise

Everyone knows exercising is a mood-booster, but not only is it hard — it can also be expensive.

Which is why it’s great that fresh research out of the UK suggests there’s a simple (and free!) way to give yourself an attitude adjustment — but there’s a bit of a catch.

The study — published Wednesday in the journal PLOS One — suggests that so-called “positive expressive writing” can seriously lift your spirits.

Rather than venting all of your frustrations, positive expressive writing focuses on gratitude, self-reflection and a vision of a sunny future for yourself.

That’s a big shift from the early days of therapeutic writing, in which participants were encouraged to endlessly rehash trauma and stress — a method the study authors say may pay off in the end, but risks digging you further down a black hole of despair in the moment.

The upbeat version, by contrast, skips the tears and gets right to the feel-good stuff.

Having analyzed 51 studies from 1930 to 2023, however, the researchers admit positive expressive writing wasn’t a slam dunk for everyone.

Some folks flourished — others didn’t budge.

Why the mixed bag? It could come down to the way the writing sessions were run — or to the personalities putting pen to paper.

Researchers say more standardized protocols and closer attention to individual differences are needed before journaling can be billed as a universal fix.

These findings nevertheless align with an increasing amount of research that shows maintaining a positive outlook on life and practicing gratitude are some of the easiest happiness hacks.

“Gratitude is mentioned in almost every conversation of happiness and with good reason — it is an emotional trump card,” mindset and meditation expert Joanna Rajendran previously told The Post.

She recommends starting small.

“While things like your health, your home, and your family all may be accurate answers, if said so generally or so often, they will no longer have the same emotional impact,” she said. “Instead, look around where you are right this moment and start with the simple pleasures and begin to list them.”

Experts also often list journaling in general as a great way to reduce everyday stress, as well as “anxiety detox” before bed.

In one oft-quoted study, people who spent just 15 minutes a day journaling felt significantly less anxiety, depression and overall distress.

So next time you’re feeling down — remember that the pen just might be mightier than the Prozac.