Editors' pick: Originally published Jan. 13.

There is a lot of preparation that goes into planning for retirement.

For many, the first part is the hardest - saving and planning for retirement. We already know that most people have saved very little for retirement and planned even less.

The next hard part, for those entering retirement, is figuring out how to make that nest egg last. One of people's biggest fears is that they will run out of money in retirement, and for many it is a legitimate fear.

And that also leads us to the third retirement challenge - and that's pulling off a successful retirement. Remember, you are figuring out how to live for the rest of your life on a fixed income. And if you don't plan it just right, you could run into big trouble.

Zaneilia Harris, president of H&H Wealth Management in the Washington, D.C. area, says it's about lifestyle.

"For the most part, it's finding harmony between your finances and current lifestyle now that they are in retirement and not bringing home the income they once had," she says. "It's balancing the dreams they once had with reality of their monthly budget. That doesn't always coincide. Even though they have opportunity to do things they waited until retirement to do, income keeps them from doing is."

Mitchell Katz, partner at Capital Associates Wealth Management in Bethesda, Md., says the biggest threats to people in retirement are not much different from the threats to people planning for retirement.

Foremost among those threats is longevity. "If you live longer, your money needs to last as long as you do," he says.

A poor or non-existent investment strategy is another threat, Katz says. 

"People in retirement sometimes have underestimated income needs," he says. "As a result, they are withdrawing more money than they should be. That is part is not having a proper investment strategy. Two numbers mater above all others - one and 30. You have one chance to put together an investment plan that will last 30 years in retirement. If the investment plan is wrong, or the withdrawal rate is wrong, it will impact their retirement."

Paul Danziger of Freedom Financial Advisors says market risk is a big threat to retirees.

"Here's what I see a lot in times of people come in," says Danziger. "Many people in retirement aren't' sure what they have. They know they have money. But many people have no idea what they have in 401(k), whether it's current 401(k) at a company they just recently retired from or from a company they worked for previously."

Of course, sometimes they know the amount they have but don't know the securities. "A lot of people don't have a plan as to how they will spend the money or grow the money," he adds.

Danziger says his firm believes in true diversity - having a portion of your money outside of the stock market.

"People come in and they are in their 70s, and they have 100% of their money invested in the stock market," he says. "I have been doing this for a long time. It was not fun in 2009 to be sitting across the table from people coming to see me in their mid-60s. They did everything right, but in one year they lost 50, 55 or 60% of everything they had ever saved, because they had all their money in the stock market. We try to have some of the money in other places."

Perhaps one of the biggest and unpredictable threats to your retirement is health care costs. "It's a big concern," says Harris.

"Not having adequate long-term-care coverage or none at all," says Katz. "That can put retirement at risk and one spouse needs care, and they spend disproportionate amount of assets, not leaving enough for remaining spouse. It's also true of health care costs."

Fidelity's Retirement Health Care Cost Estimate says that a couple, both aged 65 and retiring this year, can now expect to spend an estimated $245,000 on health care throughout retirement. That figure has increased 29% since 2005, when it was $190,000, Fidelity says.

Harris says she recommends that clients get long-term-care insurance if it is offered through their jobs. But on the private market, the insurance can be expensive for older Americans and the premium increases can be unpredictable.

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