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.

We're just a few weeks into the New Year, which means most investors' visions of market-beating 2014 returns remain firmly intact and distinctly possible. The beginning of each calendar year routinely inspires hopes, goals, and dreams far beyond the field of finance. While some people realize that a few weeks of football-induced gluttony makes their weight-loss goals much harder to accomplish, others are now starting to see the stock market eat away at their returns. That's because it's the beginning of earnings season, and no matter what the economy's like, individual stocks are more prone to volatility than usual. After reaching an all-time closing high yesterday, the S&P 500 Index (SNPINDEX:^GSPC) lost two points Thursday, or 0.1%, to end at 1,845.

Steadfast believers in Best Buy (NYSE:BBY) stock paid dearly for their faith today, as shares cratered 28.6%, a staggering daily loss rarely seen by shares in S&P 500 members. The electronics retailer shocked Wall Street by whiffing entirely on same-store sales numbers during the holidays, which fell nearly 1% from the year before. Not only did Best Buy have to lower fourth-quarter earnings guidance in the face of this, but it casts serious doubt on the turnaround narrative that drove shares to more than triple last year. I'm as shocked by the letdown as much as the rest of the market was today, but my colleague Rick Munarriz claims he saw ominous signs before today.

While CSX (NASDAQ:CSX) stock, in comparison to Best Buy, looks like nothing more than a bump in the road, Thursday's 6.8% haircut is still nothing to take lightly. Though big losses early in the year certainly make it all the more difficult to catch up with the broader market by year's end, a time horizon of 12 months to achieve your financial goals is hardly a reasonable measure of success. Railroad company CSX is a fine example of a business facing short-term headwinds (falling coal shipments, huge one-time gains that make immediate earnings growth difficult), but remains poised for long-term success.

Finally, shares of Citigroup (NYSE:C) dipped 4.4% today, despite financial statements that read like a hardcore capitalist erotic novel. Citigroup more than doubled its earnings from the same quarter in 2012, pulling in $2.7 billion. In other words, Citigroup made more money in the last three months of 2013 than the entire GDP of Lesotho in 2012 -- and Wall Street expected better. With consumer credit improving, and a global economic recovery under way, Citigroup looks primed to continue pulling in more money each quarter than the annual GDP of entire nations, although there's no guarantee investors will like it.

This article represents the opinion of the writer, who may disagree with the “official” recommendation position of a Motley Fool premium advisory service. We’re motley! Questioning an investing thesis -- even one of our own -- helps us all think critically about investing and make decisions that help us become smarter, happier, and richer.