Stocks are volatile, the economy is stagnant, and corporate pensions and Social Security seem less viable by the day. One might expect such a dismal confluence of events to jolt aspiring retirees into financial-planning overdrive, furiously making budgets, cutting spending and salting away every spare nickel.

Yet many Americans are responding to the market and economic malaise by putting their heads in the proverbial sand. Half of U.S. workers who are at least 45 years old haven't even tried to calculate how much they will need to save to live comfortably in retirement, according to a March study by the Employee Benefit Research Institute.

Others are shelving retirement dreams because they are paralyzed by fear. According to EBRI, 20% of employees say they intend to retire later than they had planned, for reasons ranging from the slowing economy to worries over the future of Social Security.

Even wealthier people are nervous. Two-thirds of "affluent investors" with at least $250,000 in investable assets surveyed in June were concerned that their retirement stash won't last throughout their lifetimes, up from 57% in December, according to Bank of America Merrill Lynch.

"People are frozen because they don't know which way to go," says Jeannette Bajalia, the president of Petros Estate & Retirement Planning in St. Augustine, Fla. "Anytime there's ambiguity, it immobilizes them."

The good news is that there are ways to fix derailed retirement plans. Among the essential tasks: talking honestly with your spouse, planning realistically for health-care expenses and rethinking your retirement age and Social Security assumptions.

The first step is to look beyond the current market realities -- volatile stocks, low-yielding bonds and slow economic growth -- and find the fortitude to continue taking measured risks.

Many investors are too rattled to invest in anything except cash these days. "There's a level of conservatism in couples in their 50s and 60s unlike anything I've seen," says Greg Sarian, a certified financial planner at Merrill Lynch for 19 years in Wayne, Pa. "Even if they already had a defensive investment posture, there's been more pullback."

Yet giving up potential growth on money meant to last the rest of your life can be risky as well. Say a couple with $2 million in savings, panicked over increasing market volatility, moves a portfolio of stocks, bonds and cash investments entirely to certificates of deposit and short-term Treasurys earning 0.5% a year and never shifts it back. Assuming they withdraw $120,000 in their first year of retirement and 3% more each year thereafter, they could run dry in about 14 years, says Michael Martin, the president and chief investment officer of Financial Advantage in Columbia, Md.

For clients approaching retirement, Martin's firm puts 28% into equities, including 22% in individual stocks and 6% in three emerging-market mutual funds. A larger portion -- 36% -- goes into six bond funds with a combined duration of less than three years and a 4% yield. An additional 16% is in cash reserves, 13% in "hard assets" (10.5% in gold and 2.5% in timberland) and 7% in a tactical fund that jumps into asset classes as conditions warrant.

This conservative allocation appeals to retirees who make portfolio withdrawals for living expenses, because their investments have some growth potential, but it also spreads risk enough to make it more likely that their nest eggs can last, Martin says.

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So far this year, the portfolio has brought a 3% return, he says, compared with the average money-market and savings account return of 0.15%, according to Bankrate.com.