Although we don't believe in timing the market or panicking over daily movements, we do like to keep an eye on market changes -- just in case they're material to our investing thesis.

More than two stocks fell for every lucky gainer in the stock market today, as January, fittingly, ended on a losing note. Major indexes suffered their worst month since May of 2012 in January. The question on the minds of many investors: "Is this just a rough start to the year or is it the beginning of a much steeper sell-off?" It's a natural question to have, but it can also lead us to stray from the long-term mind-set. Earlier this month, my colleague Morgan Housel wrote a brilliant eulogy for Long-Term Thinking, who finally kicked the bucket after the present state of financial media left him fatally weakened.

The S&P 500 Index (SNPINDEX:^GSPC) lost 11 points, or 0.7%, to end at 1,782 Friday. The index was down about 3.6% in January -- and the sun will still rise tomorrow morning.

What will not rise tomorrow morning is the price of Newmont Mining (NYSE:NEM) stock, which lost 10.4% today. While the stock performed abysmally today and lost about 50% of its value in 2013 alone, the fact that the stock market is closed on Saturdays should insulate this gold and copper stock from both gains and losses tomorrow. Newmont Mining's precipitous fall today, however, was the result of disappointing forward guidance. Although the company's preliminary results topped production expectations for both gold and copper production, the company expects gold production to actually decline from 5.1 million ounces of gold in 2013 to 5 million ounces of gold in 2014. With the price of gold still struggling, there wasn't much to cheer for on Friday. 

MasterCard Incorporated (NYSE:MA) also took a hit on Friday, slipping 5.1% after last quarter's sales and earnings failed to impress. I still think MasterCard is poised to outperform for patient, longer-term investors, since cash, as we know it, is slowly becoming an antiquated inconvenience. Its "disappointing" revenue growth was still 12%, which isn't bad for an $87 billion behemoth. MasterCard slowly lost customers to Visa last quarter, which shouldn't be a long-term trend, but is something shareholders should still watch closely.

Lastly, shares of the Sunnyvale, CA-based communications technology company Juniper Networks (NYSE:JNPR) shed 4.5% Friday. There was no compelling reason for the stock to sell off. Sometimes, the recent success of a stock can work against it, and this may be what we're seeing from Juniper Networks shareholders today. Even after today's losses, the stock is up nearly 18% in 2014, the result of two activist hedge funds taking large stakes in the company, as well as fourth-quarter results that topped expectations for both profit and revenue. Don't be tricked by today's slide: Juniper still has quite a bit of potential in the years to come.

John Divine has no position in any stocks mentioned. You can follow him on Twitter @divinebizkid and on Motley Fool CAPS @TMFDivine.

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