Think the S&P 500's eight-month, 57% rally is safe? If you do, then you're in the minority.

A recent Bloomberg survey found that only 31% of respondents see investment opportunities; that's down from 35% in July. The picture is even worse in the U.S., where more than 50% said they are breaking out the riot shields and getting defensive.

Why all the worry? The pace and size of the rally is a big factor, since valuations are suddenly nowhere near as attractive as they were earlier this year. The memory of the financial meltdown is also still fresh, leading many to look at improving economic indicators with a healthy dose of skepticism.

In the U.S. specifically, there is a lot of concern over unemployment -- a quarter of the participants in the Bloomberg survey see the U.S. unemployment rate at 11% or more a year from now. And fretting over the fate of the dollar is undoubtedly playing its part.

Add this all up and you've got a very uneasy market that could get pessimistic enough to flip from rally to rout.

But now's hardly the time to start chewing your fingernails and taking up afternoon drinking. There are some simple things you can do to batten down your portfolio.

Sell now!
No, I don't mean everything. But many of us have stocks that we've been holding onto for the wrong reasons. Maybe it's the classic "just waiting to get back to even," or maybe it's simply a case of portfolio paralysis. Whatever the case, if there are stocks in your portfolio that you're unsure about, now may be the time to cut them loose.

Maybe it's a consumer stock like Amazon.com (NASDAQ:AMZN), whose valuation makes you uneasy, or perhaps it's a financial like Citigroup (NYSE:C), whose balance sheet makes you want to cry. It can be tough enough to see a stock decline when you have confidence in it, but there's little solace when you're on the losing end of a stock you didn't really believe in in the first place.

So go ahead, take a moment, be honest, and look through your portfolio for stocks that you're holding for the wrong reasons. I'll wait right here for you.

Buy now!
Back? OK, now that you've cut the fat from your portfolio, it's time to get some stocks in there that are not only well-positioned for the current market environment, but also poised to outperform over the long run.

One option is to look to large, stable companies that we can depend on to perform regardless of what the economy is doing. It doesn't hurt to add the additional criteria of a decent dividend, so that you get paid no matter what the market is doing. Motley Fool Income Investor picks Johnson & Johnson (NYSE:JNJ) and Procter & Gamble (NYSE:PG) are two great examples in this category.

Another option is to follow the suggestion of those Bloomberg poll-takers and scout out the emerging markets. Bloomberg noted that respondents saw the most potential in high-growth markets such as China, Brazil, and India. Obvious large-cap options to tackle in these geographies include China Mobile in China, Petrobras (NYSE:PBR) in Brazil, and Infosys in India. Of course there are plenty of lesser-known opportunities, like China Marine Food Group -- a stock identified by the Motley Fool Global Gains team -- that could be even better bets.

A final area that shouldn't be skipped is commodities. Overlapping with the emerging market growth theme, commodity producers like BHP Billiton, Freeport-McMoRan (NYSE:FCX), and Chevron stand to reap the rewards of spiking demand for commodities as high-growth economies kick into high gear. As a bonus, the commodity products that these companies sell are also a hedge against inflation.

Be contrarian
It'd be silly to think that every U.S. stock will suffer just because the U.S. is facing some headwinds. It's very likely that some investors will be handsomely rewarded for picking spots to go against the grain and invest in questionable industries like consumer discretionary or finance.

Maybe, for example, you believe that unemployment can't dampen the appeal of a couple of beers with some hot wings and a football game, and therefore Buffalo Wild Wings (NASDAQ:BWLD) will continue to charge ahead. Or maybe you're convinced (as I am) that Blackstone's high-quality franchise will help it prosper in the new world of finance.

The bottom line is that the specter of another dip in the markets isn't a cue to run and do a Chicken-Little-style freak-out. It is, however, a good reminder to check the state of your portfolio and make sure you're not sitting on a heap of stocks that you just "hope" will go up.

Check out Jordan DiPietro getting contrarian and chasing down a stock that analysts seem to hate.

Amazon.com is a Motley Fool Stock Advisor selection. Johnson & Johnson, Petroleo Brasileiro, and Procter & Gamble are Motley Fool Income Investor recommendations. Buffalo Wild Wings is a Motley Fool Hidden Gems pick. China Marine Food Group is a Motley Fool Global Gains recommendation. The Fool owns shares of Procter & Gamble and Buffalo Wild Wings. Try any of our Foolish newsletters today, free for 30 days.

Fool contributor Matt Koppenheffer owns shares of Johnson & Johnson and Blackstone, but does not own shares of any of the other companies mentioned. You can check out what Matt is keeping an eye on by visiting his CAPS portfolio, or you can follow Matt on Twitter @KoppTheFool. The Fool’s disclosure policy invented a dance called "The Chicken Little." It's currently working on a song to go with it so it can prove it's more talented than Soulja Boy.