Now, consider a college savings account, perhaps for a middle-school student. You’re reasonably sure that there will be some kind of stock market calamity between now and when the kiddo leaves home. How bad might things get?

It’s tempting to consider how you reacted to the stock market declines at the end of the last decade in figuring out how you might react in the future. If you had decent nerves back then when your child was in preschool, perhaps you were betting that you were buying stocks on sale.

That’s how I consoled myself in 2009, at least. But now that my 11-year-old is seven years away from college (or eight if she takes a gap year), riding another market wave like the one we all rode in 2008 and 2009 seems like a sure path to stomach ulcers.

How bad could things get over the next 10 years? Given how rough things got last time, I asked Howard Silverblatt, senior index analyst at Standard & Poor’s Dow Jones Indices, to calculate what people might have seen if they’d been looking back at total S.&P. 500 returns (including reinvested dividends) over a previous 10-year period. Any decade ending between January 2009 and September 2010 would have been negative, he said. In the first four months of 2009, you would have been facing a decade-long decline between 21 and 29 percent.

You’d hope that few with children about to start college were invested entirely in large United States stocks then. One benefit of diversification, as Preeti Shah, an accountant and financial planner in Matawan, N.J., reminded me this week, is that even over the four years of college, you can pull from the investments that aren’t hurting as much (say, the bond or cash portion of your portfolio) during the first year or two. Then, you cross your fingers that the stocks will recover during the latter part of your child’s undergraduate years. Indeed, stocks nearly doubled from their March 2009 lows within two years.

This summer, what felt right in my household was to cut the stock allocation in our 529 account by about 10 percentage points. That put us about halfway between what Vanguard does in its aggressive 529 account and what it does in its moderate one for people with children the same age as my daughter.

But something more conservative may be better for you. Again come the pressing questions, perhaps even more emotion-laden since they involve your son or daughter: How much more could you pay out of pocket if your college savings portfolio suffered a big loss? What if your employer cast your aging self off during the recession that might come with a big stock market decline?