I never thought a flea could teach me a lesson about investing. But something I read recently had me thinking about how we sometimes don't act any smarter than fleas do.

As I learned, the flea circuses of yore featured amazing jumping fleas that leaped to precise heights. They were trained by being kept in a jar with a lid on. They learned to not jump all the way to the lid or they would get smacked. Once freed from the jar, though, they still jumped that same height, as if the lid were still above them.

Like those fleas, we, too, get trained as we go through our investing lives. Think of your parents or grandparents (or yourself!), who lived through the Great Depression. Odds are, their behavior changed because of the experience. They may have steered clear of the stock market, for example, missing out on spectacular investing gains over the decades.

What about you?
Take a few minutes to think about what apparent lessons you may have learned from your investing experiences so far. Many of us, having watched the stock market implode in 2008 -- it fell 37% -- now wonder how much further it might fall. And we stay on the sidelines, waiting for the big rebound.

Well, that might sound good, but know that by the time it's clear that the market is recovering, it will have already done much of its recovering. In other words, you may miss out on a lot of gains. Check out how quickly some companies can rebound. The following returns are just for the three months following recent lows:

Company

CAPS Rating

Return, March 9 to June 9

Adobe (NASDAQ:ADBE)

*****

77%

CNOOC (NYSE:CEO)

****

76%

Caterpillar (NYSE:CAT)

****

62%

Flextronics (NASDAQ:FLEX)

****

126%

NYSE Euronext (NYSE:NYX)

*****

101%

Petro-Canada (NYSE:PCZ)

*****

118%

Tata Motors (NYSE:TTM)

****

225%

Data: Motley Fool CAPS, Yahoo! Finance.

Flip your lid
You may have also imposed an imaginary lid on yourself, saying there's no point trying to jump too high. Very often, we invest much more conservatively than we should. If you're 45 years old, for example, and most of your money is in CDs and money market funds, it might be relatively "safe," but it probably won't do much more than keep up with inflation. It's certainly not going to turn into a handsome nest egg for you anytime soon. Check out how much a $10,000 investment will grow to in 25 years at various average annual growth rates:

Growing for 25 years at ...

$10,000 becomes ...

2%

$16,400

4%

$26,700

6%

$42,900

8%

$68,500

10%

$108,300

12%

$170,000

Clearly, if you average 3% or 4% or even 5% with your investments, your money won't grow very quickly. Meanwhile, the stock market has averaged about 10% over long periods. (Though of course, over your long period, it might average 8% or 12% or something else.)

That's why, if you still have a long way to go to retirement, you might want to park a big chunk of your money in stocks. Remember, even if you're 50, you may have 15 years to retirement, and even then, you probably won't be cashing everything out at once. Some of your dollars will remain invested until you're 70, and other dollars won't be withdrawn until you're 75 or even older.

Look for amazing investing feats
Here's one last thing about fleas: They can reportedly jump 150 times their own length -- straight up in the air, or horizontally. That's not what we might expect, but it happens. Similarly, we might not expect to see our modest little $10,000 nest egg balloon in value until it's 150 times its original size -- $1.5 million. But it can be done.

Using an online calculator, I found that if you start with $10,000 and invest $10,000 each year and it all grows at an annual average of 10%, it'll take a little more than 27 years to reach the $1.5 million mark. Up your investments a bit, or earn a better return, and you'd hit $1.5 million even sooner.

The bottom line is that you might be able to do better than you're on track to do with your investments, if you take some time to learn a little more, think about it a little more, and perhaps tweak or overhaul your approach. Don't let the lessons you've learned throughout your investing career make you act like a flea. Instead, realize that you can jump to new heights and do far better than you have been.

Learn more:

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Longtime Fool contributor Selena Maranjian does not own shares of any companies mentioned in this article. NYSE Euronext is a Motley Fool Rule Breakers recommendation and CNOOC is a Global Gains pick. Try our investing newsletters free for 30 days. The Motley Fool is Fools writing for Fools.