Everyone knows the key to building wealth is through saving and investing. Yet last year, the U.S. Commerce Department's Bureau of Economic Analysis revealed that Americans had a negative savings rate for the first time since the Great Depression.

So why aren't people saving for their futures? While a number of excuses may be given, few are legitimate. 

"Unless you're working in a sweatshop and you're getting paid 12 cents an hour, you can save," says Rob Bennett, who writes the Financial Freedom Blog at PassionSaving.com.

Saving money Before you can stop making excuses, you've got to understand just why your argument is not valid.

6 worthless excuses 1. I don't make enough money. 2. I'll get around to it later. 3. I deserve a little luxury in my life. 4. Someone else will take care of it. 5. I'm saving through my 401(k). 6. This item or service will pay for itself.

Excuse No. 1: I don't make enough money.
"We think we don't have enough money because we're always the last ones in line," says Julie Stav, author of "The Money In You!: Discover Your Financial Personality and Live the Millionaire's Life." What's the first thing you pay when you get your paycheck? If the answer is your mortgage, your car note or your credit card bills, you're probably buying into this excuse.

One reason many people don't think they have enough to save is because they don't know where their money is going or how much money they're spending on items they don't need. "People say, 'Money just goes through my fingers,' or, 'I don't know what happened to it,'" says Stav.  If that's the case, "pay attention and bring it from the unconscious to the conscious." Once you find out what you're spending money on that you don't need, you'll realize it's all money you can be saving.

In order to make sure you save that amount, have it automatically taken out of your account before you pay anything else for the month. "The first check you write every month should be to you," says Stav. "That should go to your savings. Start with 5 percent; hopefully you can get to 10 percent. When you get a raise, put half of your raise in savings."

Excuse No. 2: I'll get around to it later.
"The answer to that excuse is: Someday never comes," says Bennett. "You get older and the more bad habits you have, the harder it is to break them."

People who put off saving and investing also don't get the benefit of time, which is one of the greatest factors in successful wealth accumulation.

"It's little by little that you're able to accumulate vast amounts of money," says Jeff Harris, founder of The Family Legacy Forum, an organization based in Lake Wylie, S.C., that helps families preserve wealth. For example, someone who starts saving $100 a month at age 20, earning 7 percent interest, would have about $380,000 at retirement age. Someone who waits until age 35 to start would have only $122,000.

Excuse No. 3: I deserve a little luxury in my life.
The purpose of having a healthy savings plan is not to deny yourself the pleasure of buying things you like today. Not only should you be saving for retirement and emergencies, but you should also reward yourself by saving for things you'll want to splurge on sometimes. If this is your favorite excuse, Stav suggests creating separate accounts for various savings goals, including occasional indulgences.