Planning for retirement means assessing your various income streams to ensure that you're able to pay the bills as a senior. And chances are, one of those income streams is Social Security. Millions of seniors count on those benefits today to stay afloat financially, and if you've spent your working life paying into the system, it's natural to expect those benefits once it's your turn to retire.

But 39% of workers aren't so sure about getting Social Security, in a recent Transamerica survey. Specifically, they're worried that benefits will get reduced or go away altogether. Are they right?

Loosely stacked Social Security cards

Image source: Getty Images.

What's happening with Social Security?

Social Security is facing its share of financial challenges. In April, the program's Trustees reported that Social Security is projected to deplete its trust funds by 2035. Once that happens, the program won't have enough money to keep up with scheduled benefits and may have to implement widespread cuts.

Why the shortfall? Social Security's main source of revenue is payroll taxes -- the taxes we all pay on our earnings, up to a certain point. In the coming years, Social Security won't manage to collect enough payroll tax revenue to fulfill scheduled benefits due to the large number of baby boomers who are expected to leave the workforce in short order. And while younger workers will be coming in to take their place, the replacement rate isn't high enough for Social Security to break even from a revenue standpoint.

Thankfully, the program has trust funds it can tap to keep up with scheduled benefits even in an absence of revenue -- kind of like how you can dip into your savings account if there's a month when your bills exceed what your paycheck delivers. But once those trust funds run dry, Social Security may have no choice but to reduce benefits substantially. Therefore, while the program is by no means in danger of going away completely, benefit cuts are very much on the table, and so today's workers have a right to be worried.

There is a solution to those fears, though: Save for your senior years independently. If you're worried about lower Social Security benefits in retirement, save enough on your own to compensate. Ramp up your retirement plan contributions, and make sure your money is invested aggressively to allow for solid growth. If you load up on stocks in your retirement plan, you're more likely to achieve that goal. In fact, if you go heavy on stocks, there's a good chance your retirement account will see a 7% average yearly return, and here's the amount of wealth you might grow as a result:

Start Saving $400 a Month at Age:

And You'll Have This Sum by Age 70 (Assumes a 7% Average Annual Return):

25

$1.37 million

30

$958,000

35

$663,000

40

$453,000

45

$303,000

CALCULATIONS BY AUTHOR.

Of course, if you're further along in your career, you won't have as many years to grow wealth, and so you may need to part with a much larger sum of money each month to mimic the totals above. But the point is to take savings matters into your own hands and not rely too heavily on Social Security for retirement income. While those benefits aren't going away, they could end up coming in much lower than you'd like or expect.