If you tell your kids to stay in their rooms until they’ve counted to 2 trillion, you’re probably not going to see them until … snacktime, when they’re bored and hungry.

But that'll give you a little breathing room to rationally think about the wallop your retirement accounts have taken over the past year or so, and what actions you should -- and should not -- take now.

Consider this: Boston College researchers compared the situations of workers who have traditional "defined-benefit" plans at work -- pensions where you get a fixed monthly payment in retirement -- versus those with "defined-contribution" plans like 401(k) plans, where you pick how much you contribute, but you don't know how much it'll grow over the years.

Over time, pension offerings have been waning, while 401(k)s have grown more prevalent. The research paper demonstrated this with some compelling numbers: In 1983, some 62% of workers had just a defined-benefit plan, while 12% had just a defined-contribution one. By 2004, that had been roughly reversed, with 63% of workers having just a defined-contribution plan and 20% having a defined-benefit one.

The researchers found that between Oct. 9, 2007, and Oct. 9, 2008, American households saw the value of their 401(k) plans and IRAs shrink by a whopping $2 trillion, while the value of their defined-benefit plans decreased by $1.9 trillion. (Note that with the defined-benefit plans, the shrinkage is generally the problem of the employer, not the employee.)

What to do
Seeing those huge numbers drove home the magnitude of losses born by many Americans. I realized that many people have probably sold out of their stock holdings, realizing big losses and deciding that this is not a good time to be in stocks. After all, many familiar names, such as Boeing (NYSE:BA), Texas Instruments (NYSE:TXN), and Schlumberger (NYSE:SLB), fell 50% or more in 2008. Sun Microsystems (NASDAQ:JAVA) lost nearly 80% of its value.

The problem is that selling may end up burning them. If you believe that our economy will recover, that stocks will resume their upward trend one of these days, rethink your decision to be out of the market -- because no one really knows when the market will start heading up again, and you'll pay if you're out of it on some critical days when it makes some big moves.

Imagine, for example, that your $100,000 nest egg had shriveled to $60,000 and you sold it in a panic. If you wait until the market rises 15% before you're convinced you want back in, you will have lost out on a $9,000 gain from your $60,000.

Often, the market doesn't give you a second chance. But with share prices still low, even if you panic-sold over the past few months, think about whether you're ready to get back in. Maybe talk it over with the baby while the older kids are still in their rooms counting.

Longtime Fool contributor Selena Maranjian does not own shares of any companies mentioned in this article. Try our investing newsletters free for 30 days. The Motley Fool is Fools writing for Fools.