You're delusional.

No, it's OK, we all are.

Think about your gym, which you visit so infrequently you’re practically making a charity donation to Bally Total Fitness. Or the diet cleanse you spent $100 on ... when you could have paid $30 in healthy groceries that would have also done the trick.

Don’t kick yourself—you’re not alone in falling prey to these marketing ploys. There’s a reason that, for instance, the burgeoning “enhanced waters” beverage category (think Vitamin Water) has become a $1.5 billion industry.

By playing on our delusions and our fears, companies tempt us to shell out for needless items, and that can wreak havoc on our finances, if we let it!

Watch out for these seven industries that profit from our insecurities—and find out how to resist their ploys.

Gyms

No industry plays on the chasm between what we do and what we wish we did better than the $21 billion fitness club industry. At the beginning of a fitness push, we are all too happy to hand over a hefty membership fee and sign a yearlong contract, hoping the sunk cost will encourage us to create whole new selves.

But the reality is that 67% of people with gym memberships never use them. Even those who go to the gym regularly are paying a lot more than they imagined: A U.C. Berkeley study showed that people who signed up for a monthly gym membership ended up paying 70% more than they could have paid on a pay-per-visit plan available at the same club.

The reason? “Overconfidence about future self-control,” say the researchers. In other words: Delusions. 

Tip: If this is you, find out the best workouts for you and your budget. Even if you do actually use the gym, make sure you're getting the best deal possible: comparison shop, use a competitor's price to get a deal at your preferred gym, or sign up for a yearlong membership to get the best possible rate.

Health and Diet Food

In 2011, the market for vitamins and supplements was $28 billion—despite a lack of solid research proving their effectiveness. In fact, most of our food is fortified with nutrients, so once-common deficiency diseases are now rare. Most researchers say that unless you're pregnant or elderly or have an identified deficiency, you don't need supplements and that a balanced diet is the best source of nutrients.

As for the weight-loss market, which in 2010 was worth $60 billion, several studies show that dieting actually consistently correlates with future weight gain.

Tip: If you're a sucker for vitamins and supplements, don't pay a premium for packaged foods making health claims; eat these superfoods instead. And if you think your ticket to weight loss is a diet program, consider preparing meals from fresh, whole ingredients and setting up a regular exercise routine to do it on your own instead.

Electronics Rebates and Warranties

Electronics store ads often advertise a new gadget’s price as if you’d already received all the mail-in rebates. But a Consumer Reports survey found that less than half of people always or often cash in on rebate offers, and a full quarter never do. Even among those who sent in for their rebates, 21% said they never received them.

Additionally, extended warranties and insurance plans for smartphones sound so sensible. But they're almost never a good deal, consumer advocates warn. The extended warranty business itself generates $15 billion a year of almost pure profit, playing on our innate urge to avoid losses even if we could financially afford to replace the object.

And consider this: By the time the manufacturer's warranty ends on your phone, laptop or other high-tech gizmo, you'll probably want to upgrade to a newer model or the replacement price will have dropped, making the extended warranty moot.

Tip: Before you rush to take advantage of a deal you can only get with rebates, ask yourself: Are you going to diligently fill in every form and mail the thing in on time?

And next time the cashier asks you if you want to pay 10 to 50% extra for an extended warranty, just say no.

Apparel

According to a recent survey, a woman owns 22 garments she never wears.

And that adds up: Americans spend $331 billion a year on clothing (which works out to $1,100 per person a year). While every once in a while we all really do need a new item of clothing, you could probably easily identify a number of pieces in your closet that you never wear—and they probably add up to a lot of wasted dollars.

How does this happen? We tend to invest in the same items over and over (whether ten black sweaters or a dozen flirty sundresses). Another problem: We buy for the life we want to have—cocktail dresses for parties we never go to, or fancy new workout clothes for the gym we never visit.

Tip: Host a clothing swap to get rid of the chaff in your closet and bring fresh inspiration in, and go on a clothing fast for six months to force yourself to get creative with what you have. Need some ideas? See how one editor dressed herself for one month with just six items of clothing.

Cleaning Products

Have you ever bought different cleaners for your floors, your furniture, your bathroom and your windows? Then you can understand how the cleaning product industry rakes in $52 billion a year.

Commercials for household disinfectants and other cleaning products would have you believe that illness-causing germs linger on every surface. But experts warn that routine use of disinfectants is not only unnecessary but harmful, especially when harsh chemicals are used.

Tip: You can get your home sparkly-clean—and with less harm to the environment—using inexpensive combinations of baking soda and vinegar. In fact, we can show you how to tackle 40 household tasks with just these five everyday products.

Baby Products

Certain baby products really do ensure infant safety, like car seats. But companies also milk extra money out of parents' desires to give their kids the most organic, least toxic, most brain-enhancing food, toys, clothing, bedding and more.

Previous generations somehow survived infancy without shopping cart liners, video baby monitors, tiny shade tents for sunny days at the park and many of other items that make up the $7 billion Americans spend on today's babies.

Tip: Stick to essentials and learn how to save on baby stuff with these 12 tips. Want to really overhaul the way you handle the baby portion of your budget? Check out our Baby on Board Bootcamp, which explains what you should buy new, what you can get used and which safety considerations really matter.

Pet Products

Americans spent an estimated $53 billion on their pets in 2012, a number that's grown nearly 30% in the past five years, even as the economy tanked. Last Halloween, pet owners were projected to spend $370 million on their pets' Halloween costumes—a 40% increase from 2010.

Several factors account for the rise in pet spending: Americans have a third fewer friends than they did 20 years ago and the number of Americans living alone—one in seven—is at an all-time high. These trends partly explain why about four in five animal owners think of their pets as children, and 58% even call themselves the "mommy" or "daddy" of their pets.

This higher status of pets in the eyes of their owners has even resulted in one million dogs being named beneficiaries in their owners' wills.

Tip: Be realistic about how much your pet costs, and be sure to budget for any extra splurges or treats. As for whether to name him in your will—clearly that depends on what you think of his money-managing skills.

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