LOS ANGELES  — We cherish things and accumulate them. We move them from shelf to shelf, and from home to home. The federal government estimates that a quarter of Americans with two-car garages don’t use them for automobiles. Even those without a permanent home carry their stuff around with them.

We like to shop, own, trade or give away. Things matter to us, for reasons practical and emotional.

“Our possessions all have magical qualities. Many, if not most, of the things we keep have an essence that goes beyond the physical character of the object,” said Randy Frost, a professor at Smith College, in Northampton, Mass., who has studied and written about hoarding and is the author of “Stuff.”

A stroll through the Sunday flea market outside Fairfax High School provides a catalog of some of those magical objects: varsity letter jackets, rotary phones, typewriters, fur blankets, old ties and cowboy boots. Butterflies pinned to cardboard and framed. A crystal Eiffel Tower. A blue guitar.

Vendors collect stuff to sell to people, who often resell the stuff all over again.

“This market has the best eclectic stuff — a collection of people’s things that are old,” said LaNell Petersen, shopping on a recent weekend with her sisters. She likes the hunt for something she believes is more valuable than its price.

Consider these statistics cited by professional organizer Regina Lark: The average U.S. household has 300,000 things, from paper clips to ironing boards. U.S. children make up 3.7 percent of children on the planet but have 47 percent of all toys and children’s books.

So why can’t we let go? And what are the implications of our reluctance to pare down, our inability to get organized?

The notion that things don’t matter is rubbish, the experts say. They matter for many reasons: keeping up with the Joneses, recalling departed loved ones, even objective value — like the 17th century Dutch painting that is among many objects of desire in Donna Tartt’s “The Goldfinch.”

Our things can give us a sense of security, connection to the past, to the people we love.

“When you go home in the evening after work, you go in your house and you feel comfort because you have your stuff,” Frost said.

But that security may be a crutch too, “a sort of public artificial mask,” said Andrew Mellen, a professional organizer and author of “Unstuff Your Life.” “Full bookshelves say, ‘I’m well-read. I have lots of books.’ But really, you just buy books. Is your home an accurate external reflection of you?”

Lark had bookcases full of the books she used to earn a doctorate in history. When she downsized to an apartment, she looked at the volumes and came to the conclusion that they represented her accomplishment, her intelligence. As she decided what to keep, “I had to ask myself a lot of questions. Who am I without these books? What will people think of me? Getting rid of them, am I less smart?”

Finally, she passed them on to a younger doctoral student and said she’s happier for it.

But there’s no single prescription: “One person is happy living in a sparsely furnished yurt,” said Gretchen Rubin, who devoted a chapter of her book “Happier at Home” to assessing her possessions, “while another person is happy adding to a collection of fine porcelain. There’s no one right way.”

“I don’t think stuff is inherently wrong or bad,” Mellen said, “but if things have become obstacles to your happiness, that’s a problem.”

Figuring out what to discard and being able to actually toss stuff is crucial to an ordered, happy life, experts say.

“I am impressed by the degree to which outer order controls inner calm,” said Rubin. She recalls the friend who told her, “’I cleaned out my fridge, and now I can change careers.’”

Among our keepsake possessions, photos have their own “symbolic weight,” prompting people to save even pictures of people they no longer remember, Rubin said.

Eventually many of them end up in the trash — unless Mark Kologi gets his hands on them. For 17 years now, artists in need of inspiration and all sorts of other people have found their way to his flea market stall to root through bins of miscellaneous snapshots, most of which sell for 50 cents apiece. He estimated he’s sold millions over the years. “They don’t belong in the garbage,” he said.

Some have been bought by Luiso Berdejo, who was inspired to make the film “Violet” by one picture. In the film, a young man falls in love with a woman he sees in a photo from that stall and sets out to find her.

As Berdejo talks, another customer encourages a friend to “just reach in and pull one out.” You never know where it might lead.

A few tips on how to figure out what to save and what to toss among your worldly possessions.

Should you save it? Deciding what to buy, what to keep and what to toss “takes a lot of mental energy,” said Rubin. Here are some questions to ask yourself, and some tips for dealing with too much stuff.

1. Is it truly meaningful? Just because you picked up a seashell in France doesn’t necessarily mean it reminds you of the trip there, Rubin said.

2. Is it containable? Consider a thimble to remind you of a grandparent rather than, say, a table.

3. Is it part of a collection? When people amass a bunch of something, such as coins or Disney figurines, they start to seem more valuable. Don’t be fooled. That still may not make them worth keeping.

4. “Why not surround yourself with just that which gives you pleasure? With love and beauty and things that fill your heart and mind,” said Lark. “Like clothing. Keep what makes you look hot. But if it’s only OK, why keep it?”

5. When an object appeals to you. Ask yourself what you’ll do with it, where it will live, whether it will replace something else. And sometimes you might conclude that “it’s enough that it exists in the world” and you needn’t own it.

6. Was it a gift? A freebie? Just because someone gave it to you doesn’t mean you have to keep it, Rubin said.

7. “Anything that deepens relationships with other people” is worth owning, Rubin said. That could be an origami set to use with your child or fancy kitchen knives used to prepare dinner parties.

8. Worried that you have too much stuff or care too much about it? Worried that you might be suffering from “affluenza”? There are resources if you want to pledge to buy nothing new for a year except consumables.