I learned that lesson after I glanced at my mortgage statement one month. I typically add a little extra to each payment so I can whittle down the loan faster and save on interest. (Another good reason for taking charge of your finances—but that’s another story.) Usually any overpayment is assigned directly to principal, reducing my loan balance.

But that’s not what happened this time. According to the statement, an extra $110.53 of my most recent payment was assigned to escrow—the funds the bank sets aside for property taxes and home insurance.

I was surprised, to say the least. I hadn’t been told there was to be an increase in escrow. But I assumed there must be some reason for the change. After all, what do I know about mortgage amortization and escrow accounts? I shrugged it off, but made a mental note to check my statement again the next month.

Again, the same increase in escrow.

I called the bank to ask why this allocation that I did not understand had been made for the last two months. To my amazement, I was told that the bank had simply made an error in allocating my payment.

Had I let this error stand, I would have paid more interest on my mortgage than I should have—at least until the end of the year, when hopefully the surplus in the escrow account would have been noticed. (Or would it?)

So why am I telling you all this? Because this incident illustrates several important principles of generalism:

Value your own knowledge. The first time I noticed the discrepancy on my statement, I knew it wasn’t right. But I didn’t trust my own knowledge. I just assumed the bank employees knew what they were doing. After all, they’re the experts in money matters, right? Well, yes, but they’re also human and can make mistakes.

Take ownership. When the error occurred, no one at the bank noticed. To them, it was just one little blip in a sea of numbers. But it’s my home, my mortgage, and the payments come out of my budget. So it’s my responsibility, as the owner in this situation, to keep a close eye on what’s going on.

Become empowered. The second time I noticed the discrepancy, I empowered myself to do something about it. In other words, I picked up the phone and called the bank. Some people might not have bothered. Why deal with all that hassle just to save a few bucks on interest? You can decide for yourself, but here’s what I know: Wealthy people didn’t get that way by allowing someone else to make mistakes with their money.

Hold experts accountable. Although it’s my responsibility to take charge of my money, the bank also has a responsibility: to handle my funds properly and according to my wishes. Once I pointed out the error, I held the bank accountable for fixing it. The surplus from the escrow account was applied to the loan principal, reducing the balance and saving me interest.

Not reading your banks statements saves time. But allowing someone else to manage your money—especially an impersonal institution like a bank—can cost you. Is it worth it? Not in my book.

Generalists trust in themselves and what they know about the world. Here are five household names who have done it well:

Oprah Winfrey. She doesn’t have a political science degree but that didn’t stop her from helping Barack Obama seal the 2008 Presidential election. She’s not a teacher but founded a successful school; not a writer but has one of the most successful magazines in the US to her credit. And the fact that she’s not a licensed therapist didn’t matter at all to the millions of people who were touched by her talk show over the years.

Steve Jobs. Most inventors are lucky to have one household appliance to their credit. Jobs’ vision brought us the computer on your lap, the iPod in your car, the iPad in your hands, and the smartphone in your pocket. Apple’s hallmark of creating relevant, functional, indispensable products is in large part due to the fact that Jobs remained personally involved and invested in each. Instead of specializing in the business of being a CEO, he was constantly learning about what people really want and need, even to the sometimes startling extreme of answering his own email.

Al Gore. Had Al Gore limited himself to specializing in politics, he would have been a footnote in history. Instead, he is the recipient of a Nobel Peace Prize, a respected author, and a dedicated environmentalist. Sometimes a generalist’s path emerges later in life, but the key point is the same—a broad knowledge base and versatile skills bring opportunity.

Martha Stewart. The name of her company, Martha Stewart Living Omnimedia, says it all. From an early career that ranged from model to stockbroker to caterer, Stewart has followed her passions to become the ultimate entrepreneur. Her taste reigns 365 days a year, from weddings and holidays to kitchen basics, crafts, and kids. If Stewart had to specialize in just one thing, it would probably be success.

Richard Branson. The ultimate modern Renaissance man, billionaire Richard Branson didn’t just start a company—he pioneered a brand. Rather than specializing in one area, Branson’s Virgin Group is at the center of over 400 enterprises, from music and airlines to beverages and cell phones. He has his hands in comic books, health care, online games, hotels, green technology, and more, and that’s just his business life. An adventurer, philanthropist, and public figure, Branson never put limits on himself, despite dropping out of school at age 16. “Business opportunities are like buses,” he’s quoted as saying. “There’s always another one coming.”

So what’s the big idea here—That only celebrities can be successful generalists? That generalism is the path to becoming a multimillionaire? Of course not. But these five individuals prove beyond a doubt that specialism isn’t the only path to success. The next time someone pressures you to focus on just one narrow field or sneers at your lack of “expert” credentials, just smile and think of Oprah.