Tracking your expenditures for several months as you get closer to retirement will help you get a better handle on what you might need — particularly if you consider such factors as whether you plan to travel more, or whether your car will need to be replaced once you retire.

Then there's Social Security. Trusting what the Social Security website predicts you'll receive can be a dicey proposition, it said, pointing to the projection that the Social Security trust fund will be depleted by 2034. By how much might that reduce your benefits and how much are you counting on them?

Pensions might not be such a sure thing, either, since many companies are freezing pension plans — and if you can't stay with your employer long enough to be vested, that will affect what you might be able to draw on, too.

Oh, and if you're planning on a job during retirement, you might want to rethink that as a sure thing: 48% of retirees who want to work aren't, 35% are unemployed for health reasons, 5% provide care to a loved one and 8% just couldn't find work. Even if you plan to work until age 65 you might not be able to, due to ill health or because your job just disappeared. That means you'll have less time to save and more time to spend.

Then there's the good news: You might live longer. The bad news: You might outlive your savings.

Then there are those pesky issues around your investments: Expected return (usually estimated high) and confusing investment returns with income. In the former case, projections of 7% to 10% returns are likely too optimistic, given low interest rates, market volatility and other factors. An estimate of less than 5% annually would be more realistic. Even if you make that 5%, though, that doesn't mean you can take the whole 5% out every year. Doing so could deplete the principal, which could run you out of money sooner rather than later.