In 1765, the daughter of French philosopher Denis Diderot was engaged.

But Diderot was too poor to provide a dowry. So he sold his collection of books, known as La Encyclopédie, to Catherine the Great for a great sum of money.

Suddenly flush, he paid a handsome dowry for his daughter and bought a beautiful scarlet cloak to celebrate his fortune.

That’s when his mind became a hellhole of compare and despair.

The more he looked at his scarlet cloak, the more dowdy and unappealing the rest of his possessions appeared.

So he bought some hip shoes to match the coat.

Then he added an expensive hat with a feather.

He upgraded to a better mirror and better lighting.

More candles revealed a shabby chair that had to be replaced and … you get the picture.

In his essay entitled “Regrets on Parting with My Old Dressing Gown,” Diderot writes, “I was absolute master of my old dressing gown, but I have become a slave to my new one.”

Psychologists describe the Diderot Effect as “the introduction of a new possession into a consumer’s existence that often results in a process of spiraling consumption.”

Humans have an unhealthy propensity toward over-consumption, mostly because it feels good in the moment.

Buying stuff activates the nucleus accumbus, the brain’s reward, pleasure and addiction center. This makes spending money a non-stop thrill ride.

But, of course, the ride ends almost as soon as we hang up the new coat in the closet. So we get back at it, spending more money and accumulating more stuff.

If you throw that credit card around thoughtlessly, you short-circuit the prefrontal cortex and award the amygdala decision-making power.

Your amygdala does not make a good financial advisor; it will always tell you there isn’t enough, what you already own isn’t good enough, you yourself aren’t good enough.

The nucleas accumbus jumps in here too, whispering that real happiness only lies one purchase away.

You senselessly throw things in your cart, feeding the beast, always hopeful this shirt or this car or this gym membership will fill that hole.

It’s another arrival fantasy, a quick fix that doesn’t last.

Mindfulness puts to rest the damaging mental processes that drive unhealthy consumerism, allowing us to be content with what we already have, lifting the veil on the illusion that more will make us happier, giving us greater control over impulsive spending.

Mindfulness creates greater awareness in all aspects of our lives, including awareness that our spending decisions impact our selves, our communities and the planet.

We become more mindful of how we spend our time, energy and money.

There is a current trend toward minimalism, the idea that organizing our physical spaces makes us calmer and happier.

But without a mindfulness component, tidying up only supplies fleeting happiness.

Wonder why?

Merely touching an item creates an emotional attachment to it.

This is why Apple stores are designed for you to physically touch the devices; moving the mouse on Apple’s new laptop tells your brain it’s already yours.

This ownership experience sells more laptops. This same ownership experience destroys your decluttering efforts if you aren’t being mindful.

When cleaning your closet, let’s say you find a sweater you rarely wear.

Part of your brain says, “Let it go. It’s just taking up space.” Another part of your brain fights this, saying, “You paid good money for this sweater. Better hold onto it.” The longer you actually hold it, the harder it is to add it to the Goodwill pile.

Mindfulness helps to mitigate this argument by illuminating the narratives, beliefs, behaviors and illusions you hold about your possessions.

It’s less about having an Instagram-ready Tupperware drawer and more about examining your beliefs around material possessions.

Without mindful awareness, you abandon the closet cleaning for a Target trip because you just realized you cannot live another day without an over-the-door scarf organizer, a shoe basket that slides under the bed or a cabinet bin to house your pot lids.

Suddenly, your intentions for a tidy and organized home create a new desire to spend money.

Here’s what I’m learning: Our brains trick us into thinking we need more stuff than we do.

Get in the habit of praying before paying, or taking a mindful minute before you buy something superfluous.

When you see something you want to buy (something that you really want but don’t necessarily need), take 20 deep breaths, counting them as they pass.

Pause to notice why you’re spending and how that particular expenditure makes you feel, creating an opportunity to change old habits and make new choices. Observe when you are being drawn into spiraling consumption.

It might seem odd to close your eyes at Target and breathe for a bit, but who cares?

It is too easy to confuse who you are with what you have. Possessions do not define you. You define you.

Erin Smith is the owner of the OM place in Winchester, the author of “Sensible Wellness” and the online host of the OM channel. Follow her on Twitter @erinsmithauthor.