But some retirement experts have found that an even more conservative mixture at retirement may be ideal. What they suggest next is counterintuitive, but underscores the long game that is the stock market: Instead of maintaining that lower allocation to stocks, they suggest you gradually increase it as you age.

A study from 2013 found that portfolios that started with about 20 to 40 percent in stocks at retirement, then gradually increased to about 50 or 60 percent, lasted longer than those with static mixes or those that shed stocks over time. The analysis was conducted by the retirement experts Wade Pfau, professor of retirement income at the American College of Financial Services, and Michael Kitces.

Certainly, such a strategy could backfire, especially if you have trouble sticking with it. But becoming too conservative introduces another set of risks: Maybe the money won’t last as long as you do, or it won’t grow enough to offset inflation. For Americans who are 65 now, the average life expectancy is 84.4 years, according to the Centers for Disease Control and Prevention. There’s also a strong chance those Americans will live into their 90s. That longevity calls for a decent helping of stocks.

So what do I do?

If you haven’t retired yet, there are some simple ways to give your portfolio some breathing room. Working a little longer, even part time, is effective when that’s possible. And if you’re able to postpone collecting Social Security, that’s another way to guarantee a higher paycheck in retirement over the long run.

If you recently retired, what’s your next best step? First, consider what your portfolio mix looks like now — the recent market mayhem may have brought your overall asset allocation to a more conservative place, and maybe it makes sense to maintain that for now. If you have a significant chunk of cash, or another source of income outside your portfolio, experts suggest tapping that money in times of market turbulence instead of selling stocks.

“A really simple rule that I found works quite well and does just as well as more complicated rules, is that you just look at your portfolio balance on the date you retired,” said Mr. Pfau of the American College, which trains financial professionals. “Whenever the current balance is less than that number, draw from the buffer asset. Otherwise, you withdraw from your portfolio. This is simple and works well.”

Besides cash, investors with a whole life insurance policy — which typically includes a cash savings component that can be tapped — can potentially borrow from that pot of money, he said. (It is later repaid by being deducted when the death benefit is paid out.)