We live and die one catchphrase 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 GameStop (NYSE:GME) for half of today's price two years ago. The stock wasn't cheap back then, either, since the company was already the leading video game retailer.  

However, the market didn't fully appreciate what the new generation of video game consoles meant for the chain. More important than just the obvious upgrade cycle, GameStop's thickest margins come from reselling used gear. In other words, diehard gamers sell their old systems to GameStop, where the markups are higher. The market presented opportunities to cash in on the software companies that created surprisingly successful titles like Take-Two Interactive's (NASDAQ:TTWO) BioShock and Activision's Guitar Hero -- but GameStop was there to cash in no matter what was selling.

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"
GameSpot sported a high P/E ratio through most of its run. Take-Two -- a Motley Fool Rule Breakers recommendation -- has rarely traded at a market discount. The same can be said for iRobot (NASDAQ:IRBT), another pick in the growth-stock newsletter service. The military and consumer robotics specialist has a high valuation because it's not earning a lot of money in this early stage of its growth cycle. The company's Roombas are sucking up dirt in your living room. The company's PackBots are sucking up roadside explosives in Iraq. The big profits will come to those who wait.

Stay ahead of the pack, and rearview 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're seeing it now with Akamai (NASDAQ:AKAM) winning patent battles with smaller competitors. Investors who feel that the good news is the end of the gravy train fail to realize that court victories have far-reaching implications. This particular case may help Akamai establish a sustainable advantage in a once-cutthroat industry.

"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 the time with companies such as GameStop. 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 eating out anymore? Tell that to IHOP (NYSE:IHP). The pancake-flipper continues to post positive comps, even with nondiscretionary income drying up. No one is shopping anymore? Check out lululemon athletica (NASDAQ:LULU). The yoga apparel chain is posting double-digit comps gains.

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.

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

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. Take-Two Interactive, iRobot, and Akamai 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.

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. Activision and GameStop are Stock Advisor picks. The Fool has a disclosure policy.