We live and die one catch phrase at a time. We can't help it. Mantras feel so good as they roll from our tongues. We cling to them because they're catchy, like cotton candy on sticky fingers.

We can be so stupid sometimes.

OK, let me narrow that down. I can be so stupid sometimes. I've been seduced by market poetry. I've accepted a battle cry like "bulls make money, bears make money, but pigs get slaughtered" as a Wall Street truism. But maybe it's time I stick up for this little piggy that went to market.

I understand why bulls make money. There's a historical advantage to going long. Daily downticks and corporate meltdowns show how bears make money, even if it's a trickier practice, given the market's tendency to inch higher over long stretches of time.

But I get lost with this obsession with turning a pig into canned pork product. What's the problem here? Are you a glutton at the feeding trough if you hold on to a company for too long? Of course not. Great investors like Warren Buffett have held winning stocks for generations. Are you piggish because you hold a 10-bagger with the hope that it will roll into a 20-bagger? If so, hold your snout up high, because some other nervous Nellie cashed out earlier when it was just a five-bagger.

I would argue that "bulls make money, bears make money, pigs make more" is a better slogan. Yes, it sounds hedonistically stubborn. There's a certain stench of Gordon Gekko arrogance in claiming that greedy investors come out ahead. However, history teaches us that there are times when it's good to be a pig.

Investors were scooping up shares of Apple (NASDAQ:AAPL) for a third of today's split-adjusted price two years ago. The stock wasn't cheap back then, either. The company's signature iPod was already the established giant in digital music. The "halo" effect that was propping up Mac sales as a result of its musical hipness was well documented.

However, whether the market felt that Microsoft's (NASDAQ:MSFT) Zune would challenge Apple, or that the music subscription model championed by Napster (NASDAQ:NAPS) would take off, the market's apprehension fed Apple just fine. 

Well played, piggies.

When pigs fly
That got me thinking: If that sound bite is flawed, how many other morsels of investing wisdom come with hollow centers? How many people boil down market philosophy to four simple words that can burn them in the end?

Way too many, I'm afraid. My good friend Bill Barker has done a great job of singling out four-word philosophies that work; now I've unearthed my own set of less-fortunate maxims. See whether any of these have burned you as badly as they have scorched me in the past.  

"The P/E is low"
Stocks aren't cheap just because the multiples on their trailing earnings are low. Homebuilders have low price-to-earnings (P/E) ratios on a trailing basis, but some pretty sobering markups if we look ahead. Utility stocks may trade at low prices, but the same can be said for their growth prospects. A stock with a low P/E is not necessarily cheap.

"The P/E is high"
Apple sported a high P/E ratio through most of its run. Motley Fool Rule Breakers recommendations such as robotic arm surgical specialist Intuitive Surgical (NASDAQ:ISRG) and quick-service burrito shop Chipotle (NYSE:CMG) always seem to go for market premiums. The key here is that they are both growing quickly. Intuitive Surgical continues to wiggle its way into more operating rooms after proving its hospital benefits. Chipotle has gone through seven straight years of posting double-digit comps.  

Stay ahead of the pack, and rear-view numbers can be deceiving. A stock with a high P/E is not necessarily expensive.

"Sell on the news"
Speculative investors buy on the rumor and sell when they're right, but where's the joy in that? They took on the risk that a certain event would take place, but they're not going to stick around to enjoy the spoils of victory? You saw this happen when Google (NASDAQ:GOOG) went public in 2004, with investors fretting over the moment that the lockup period expired and insiders could begin selling. It failed to happen in a materially damaging way.

You also see this happen every time Apple seems to bump up against a competitive threat. In the end, it either comes up with a better mousetrap or outclasses its rivals.

"Buy low, sell high"
This is probably the most overused tidbit of market jargon. It ignores the obvious: We often don't know what defines too low -- or too high -- until it's too late. Hitting a fresh 52-week low is rarely the sign of a trough. A new 52-week high is unlikely to be a peak. You see this all of the time with companies such as Intuitive Surgical, Google, and Chipotle. Fresh highs aren't permanent peaks. If anything, a year later, they often start being referred to as a 52-week low.

All hogs go to heaven
So where does that leave you? I hope you haven't tethered your life to an arsenal of clever, empty words. Few market truisms are universal. Look around long enough, and you'll find more exceptions to the rule for any prolific claim.

Stocks march to their own beats. No one is going out to eat anymore? Tell that to Texas Roadhouse (NASDAQ:TXRH). The casual-dining steakhouse chain is on a roll. Many of its peers may have succumbed to empty dining rooms or desperate buyout offers, but comps keep climbing at Texas Roadhouse. In a world where diners' tastes are fickle, that's amazing.

I don't follow the guidelines in seeking out my next stock purchase. I know that rules are perpetually broken. I'm smarter than that.

OK, let me broaden that a bit. We're smarter than that.

Want a four-word phrase that may make you rich, instead? Why not give Motley Fool Rule Breakers a shot? The newsletter service picks promising stocks that are reshaping the competitive landscape. Chipotle and Intuitive Surgical are active recommendations. And even though "there's no free lunch" is another popular four-word phrase, I'll let you in on a free 30-day pass to eat as much as you like.

This article was originally published on April 10, 2007. It has been updated.

Longtime Fool contributor Rick Munarriz doesn't like to speak in four-word sentences. Well, maybe this time. He does not own shares in any of the companies in this story. Microsoft is an Inside Value pick. The Fool has a disclosure policy.