They seem so right! So true! And yet...they're not. Discover your own magical thinking about your finances.

1. "The bills aren't my job."
I'm unfortunately very familiar with this lie. When the recession sunk its claws into our lives, and my husband, Dan, was left unemployed for over nine months before going back to school, we realized that there were some little lies we'd gotten into the habit of telling ourselves that were making it harder for us to bail out. By then we'd had our first child, and the combination of the recession and becoming a mom all in a matter of months had left me overwhelmed. One night, when my son was two weeks old, I said to Dan: "I can't do the bills anymore. They have to be your job." Now, it's true that busy families often divvy up the tasks—"You clean the kitchen while I put the kids to sleep"—and the bills can feel like just another one of those parceled-out chores. Except here's the problem: Dropping that mountain on one person's shoulders, especially during tough times, and thinking that they'll be able to manage it while you enjoy some blissful ignorance can lead to even more stress. It's really important that both people in a partnership know what's going on with the finances. Although Dan took over with aplomb, we soon realized that we needed to put our heads together and strategize. Soon, the cliff before us felt scalable.

2. "If I order takeout, I can eat half tonight and half tomorrow—that's two meals in one, and it actually saves me both money and time."
Although takeout has never been a huge part of my life, I have a lot of sympathy for this kind of magical thinking because I can't count the amount of times I've thought it was "worth it" to buy coffee or a snack when I could easily have packed the rest of my morning's coffee into a thermos, grabbed an apple and put a few slices of cheddar into a Tupperware. The bottom line is this: No prepared drink or food is ever ever going to be cheaper than homemade, no matter how much time you save, no matter how you slice and divvy it.

3. "The cost of an ATM fee (three bucks) is less than the cost of my time running around to find my own bank."
Once you've talked yourself into the fiscal soundness of saving a few minutes at the ATM in McDonald's (which is not your bank!), you will justify the cost over and over. To turn your "calculation" on its head, consider this estimate from an organization called ATM Experts, which is trying to sell the idea of owning an ATM to business owners: "So let's figure that you have a total of 300 people a day coming through your doors, and let's say that you are charging a $2.75 surcharge per valid withdrawal...Take the middle road that 4 percent of the people that see the ATM machine will use it. Then you can count on...a minimum of 360 transactions per month at $2.75 per valid withdrawal. That comes out to $990 per month or a total of $11,880 per year. All that from one ATM machine at one location." So...someone is making money while you lose money. Sound like a good reason to take the extra five minutes to drive to your bank?

4. "I'll wear it forever..."
I met a woman at a book reading a few months ago who told me a story that really made an impression: She said that when the recession began, she told herself that for six months she would not shop for anything but the bare essentials. Everything she thought she "needed" she would either try to find a substitute already in her possession or she'd go without. Something truly surprising happened: Every time she thought she "needed" something, she'd go down into her basement—and she would find that thing or something just as good tucked away. We often trick ourselves into buying things by saying "I'll wear this or use this forever," but we've forgotten to look around and see if we already have something that might work equally well.

5. "It's good for my marriage or my kids."
I actually feel pangs of sympathy and understanding when I hear this lie because I know how much we all want to make our spouse or kids happy. Yet the truth is that if you can't afford it, you really can't afford it. Borrowing from Peter to pay Paul (or from your August budget to pay for a vacation in July) does not make good financial sense. I know you need a break, and so does your family. So here's what I suggest: Turn off your cell phone some Saturday and drive to a nearby park. Bring a picnic packed from home and some books, a blanket, a kite and some gloves and a ball. This is a break everyone deserves, and—even better!—everyone can afford.

6. "That birthday money doesn't count, so I can blow it on something I'll enjoy, not my late gas bill."
This is a particularly tricky one. Say you get a check for $100 and you know your mother is hoping you'll take yourself out for a massage with the money she gave you—heck, life has been hard!—but you also know that you owe $89 to the gas company. You feel the weight of what your mother wants for you, not to mention the idea of having this one little moment of bliss—for free! Here's the unattractive truth: The amount of stress you will relieve paying that gas bill will go further than three massages. So, take those 11 leftover dollars and drive to your grocery store and buy the nicest baking chocolate you can find, a pound of sugar, some butter and flour. Now, go home and bake yourself the best birthday cake you've ever tasted. Then call your mom and say thank you.

7. "I'll get the cheaper mobile phone plan and just keep a really close eye on my texting and talking."
Unless you've gotten a landline and ditched your cell phone because you don't have a job with a boss and coworkers who text you and don't have a teenager who texts, you are likely to text just as much this month as you did last. So if, on average, you use about 500 texts a month, pushing your plan down to 200 will not work; you will go over. And rather than saving that extra $10, you will now be charged 10 cents per text. The math doesn't lie: You have now spent $20 more.

8. "It's worth buying because I get points when I use my credit card."
Many people opt for credit cards with rewards, the most common of which are airline miles. We like the idea of shopping for toilet paper at Costco and earning miles for a vacation. But the thing is, according to Bankrate.com, most people never actually cash in their miles. A recent survey shows that 70 percent of airline miles accrued are left unused. When you factor in the unlikelihood that you actually will take a trip within the time frame in which your miles are valid (because, let's face it, trips cost more than just airfare) and weigh that against the yearly fee the credit card company charges, it becomes clear that justifying your purchase for points (or paying with a credit card rather than cash you actually have) is an elusive dream, one that belongs in fantasyland.

9. "But I got it on Groupon!"
Okay, there's a lot of discussion today about group coupons and how they give you a chance to save on stuff you love and take advantage of opportunities to do things you wouldn't normally do. This is true. Especially the "wouldn't normally do" part. I get offers in my inbox, on Facebook and on Twitter. But I'm opting out. And here's why: I recently received a one for a mani/pedi from Living Social in my email box. And I found myself clicking on it and dialing the number to make my appointment. But some little voice stopped me mid-dial. The voice asked, "Would you be scheduling that mani/pedi today if you didn't just get that in your inbox?" Although I wanted to whine, "Yes this has been on my VIP to-do list for weeks," I knew the real answer was "no." I was about to spend $39 on something that, let's face it, I really don't need, because I'm not walking down any red carpets this week. Or next.