It's never a good day to lose money, true enough. But today must have been an especially rough day to take losses, as growth in the labor market spurred big gains across the markets. All 10 of the S&P 500 Index's (SNPINDEX:^GSPC) industry groups gained today, and the benchmark index rose 15 points, or 1%, to close at 1,513. Yet Friday's three biggest S&P losers all found ways to stumble.

Business equipment maker Pitney Bowes (NYSE:PBI) led the index down, falling 4.1%. The steep decline isn't nearly as bad as it sounds, though, as long-term investors were amply rewarded with gains of more than 20% on Thursday after impressive fourth-quarter results crushed analyst estimates. Today was a classic "taking gains" type of day, which is to be expected after gains like yesterday's.

National Oilwell Varco (NYSE:NOV) was also a victim of its own earnings report. Even as profits rose more than 16% and sales advanced an impressive 33%, Wall Street was unfazed. Shares fell 3.9% Friday, perhaps because the oil driller could face "short-term headwinds." The stumble today barely hurts long-term patient investors, who have seen nearly 70% gains in the last three years alone. 

Days after the rating agency Standard & Poor's downgraded the credit in Frontier Communications (OTC:FTR) to "junk" status, the stock performed just like you would expect junk to perform, declining 3.8%. Its eye-popping dividend, approaching a 9% annual clip, has some on Wall Street worried that the company may need to cut its payouts -- never a good sign for income-oriented investors.

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