When we think about the various income sources we might have available in retirement, it's natural for Social Security to top that list. Those benefits are instrumental in helping millions of seniors today stay afloat financially.

Relying too heavily on those benefits, however, could spell trouble for those nearing retirement. But unfortunately, a large chunk of older workers may wind up doing just that.

An estimated 26% of Americans 50 and older think they can live comfortably on Social Security alone, according to new data from Nationwide. And that's an assumption that could prevent them from ramping up their savings game like they need to.

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Social Security will only get you so far in retirement

You might think you'll get by in retirement on Social Security alone, but know this: Those benefits are only designed to replace about 40% of the average worker's preretirement income.

This figure, however, assumes that benefits won't get slashed in the future. There's already talk of a 20% reduction in benefits as early as 2035 once Social Security's trust fund is depleted. If that comes to pass, Social Security will replace an even smaller percentage of income.

Meanwhile, most seniors need a good 70% to 80% of their former income to live comfortably, especially when we account for essentials like housing, food, transportation, and healthcare -- and also entertainment and leisure, expenses that aren't needs per se but contribute to a decent quality of life. Therefore, relying on Social Security alone to cover the bills just isn't practical unless you're really willing to make major sacrifices. And even then, you still may find that those benefits don't suffice in covering all of your basics.

Start saving for your future now

If you've been neglecting your savings under the assumption that you won't need retirement income outside of Social Security, it's time to rethink that strategy and instead start playing catch-up. The good news? Workers 50 and over can sock away up to $25,000 a year in a 401(k) and up to $7,000 a year in an IRA. Max out the former for 15 years, and you'll be sitting on $628,000 in personal retirement savings, assuming your investments generate a 7% average annual return during that time. (That 7% is a few percentage points below the stock market's average, so it's a reasonable assumption if you load up on stocks.)

Even if you can't max out a 401(k) -- which, let's face it, isn't an easy thing for an average earner to do -- you can still accumulate a nice amount of savings by maxing out an IRA. Doing so for 15 years will leave you with $176,000, assuming that same 7% return.