Surprise! You're probably making a bunch of money mistakes, and they may be costing you a lot -- like many hundreds or thousands of dollars.

Here's a look at five common -- and costly -- money mistakes that many people make. See how many apply to you and how much money you might be able to keep in your pocket (or your retirement accounts) by changing your ways.

Money flying out of a woman's wallet

Image Source: Getty Images

Mistake No. 1: Being oblivious to recurring charges

This mistake is easy to make because it involves expenses that are largely hidden. Unless you're in the (good) habit of regularly reviewing your credit card bills, you can easily not notice that you're being charged certain amounts regularly -- and often needlessly. (Worse still, many automatic monthly charges increase over time, too, which most people don't notice.)

For example, you may have stopped going to your local gym three years ago, but you forgot to cancel your membership so you've been forking over $40 every month. Over three years, that would amount to a hefty $1,440. Similarly, you may be paying $150 or more to your cable company each month despite streaming most of your entertainment. Cutting the cord in favor of paying for a few cheap streaming services might save you $100 a month -- $1,200 per year. You may even be paying for subscriptions going to a previous address!

Mistake No. 2: Staying at your job too long

You may think that you've done well to have stayed at your current job for many years, but to maximize your income, you might want to think about moving on.

According to Forbes, "Staying employed at the same company for over two years on average is going to make you earn less over your lifetime by about 50% or more."

The folks at human resource management company Automatic Data Processing studied data related to 24 million workers and found workers get the biggest increases in their salary when they've been at their job for at least two years but not more than five years.

An added benefit of job-hopping to boost your income is that it can also boost your Social Security benefits since they're based on your earnings history. By earning more, you'll likely be able to sock away more money for retirement.

Mistake No. 3: Not asking for a raise

Job-hopping isn't for everyone, though. Some just don't have the stomach for it, or they may simply really love the job they've got. You can aim to earn more in your current position by doing one simple thing: asking for a raise.

A recent survey from PayScale found among those who asked for a raise at work, about 70% received some sort of increase. (And by the way -- only 37% of workers surveyed had bothered to ask for a raise.)

A young woman frowns as she looks into the wallet she's opened, as lots of dollar bills fly out of it.

Image source: Getty Images.

Mistake No. 4: Not reviewing your insurance regularly

Go ahead and pat yourself on the back if you've got all the insurance you should have -- covering your health, life, car, home, and even your apartment if you're a renter. But you're not done. Insurance isn't something to set and forget if you want to keep your costs down.

Ideally, you should spend an hour or two each year contacting a variety of insurers to review your coverage for each kind of insurance and to get fresh quotes. Shopping around for better rates regularly can potentially save you hundreds of dollars per year. Insurers use different formulas to determine their rates, and the formulas can change over time. Different insurers might offer the best deal in different years. Keep an insurer's reputation in mind, too, and don't switch to one that's not rated highly.

Another way to save on insurance is to bundle your policies -- an insurer might give you a discount on all your policies if you're covered under two or more policies. Consider increasing your deductible, too. The higher your deductible, the lower the monthly premium. (Just be sure that you can afford to pay the deductible should you need to.)

According to Quadrant Information Services, raising your car insurance deductible from $250 to $500 will save, on average, about 7%. Raising it to $1,000 can save 9%, while going for a $2,000 deductible can lop an average of 16% off your premium. Of course, those are averages and some people will be able to save even more, so this is a money-saving strategy worth exploring.

Mistake No. 5: Not doing any estate planning

Finally, the last common and costly mistake many people make is putting off their estate planning. We all need to tend to this, and not just when we are approaching retirement. Even if you're still in your 30s, it's smart to have a will prepared, along with a durable power of attorney for finances, a living will, and a healthcare power of attorney (sometimes called a healthcare proxy). Even young people can end up temporarily or permanently incapacitated, and plenty of people die decades sooner than they expect to. Getting these documents and arrangements in order can save your loved ones a lot of trouble and potentially a lot of money, too. Be sure to keep your listed beneficiaries up to date for all your financial accounts as well.

The more financial errors you avoid making, the more money you'll be able to keep in your pocket -- or in your retirement coffers.