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.

Just as investors were starting to regain their confidence in retailers, after holiday sales data topped estimates earlier this week, that confidence was instantly shattered. The cause for today's 180-degree sentiment swivel was Best Buy, which disclosed its own holiday sales figures -- figures that caused investors to dump the stock and run for the hills en masse. With declining same-store sales and operating profits now likely to slump in the fourth quarter, Best Buy stock was the first major casualty of 2013's uber-competitive retail price wars. Weak results from the financial sector also pressured stocks, and the Dow Jones Industrial Average (DJINDICES:^DJI) finished down 64 points, or 0.4%, to end at 16,417. 

Wal-Mart Stores (NYSE:WMT) closed as one of the Dow's worst performers Thursday, shedding 1.2% by the ring of the closing bell. The pessimism surrounding retailers, on top of federal allegations that the company mistreated protesting employees in 2012, made Wal-Mart stock particularly vulnerable today. Shares lost ground yesterday, as well, after the National Labor Relations Board charged Wal-Mart with making "coercive statements" against workers protesting "Black Friday" policies in 2012. Wal-Mart's massive scale provides some insulation from the specter of a single disappointing quarter, but a dent to the company's reputation might prove harder to repair.

Shares of CSX (NASDAQ:CSX) fell sharply today, tumbling 6.8% after investors didn't like what they heard on the railroad's quarterly earnings call. CSX's CFO broke the news to Wall Street as management discussed fourth-quarter results on Thursday. Not only did earnings slip last quarter, but management admitted it had probably overestimated the company's growth potential in previous projections. With coal shipments continuing to trend lower, and one-time real estate gains in 2013 in mind, CSX's goal to grow earnings at a 10%-15% compound rate through 2015 looks too aggressive. 

Elsewhere in commercial transportation, Nordic American Tankers (NYSE:NAT) stock was enjoying some hefty gains, rallying 10.8% in trading. Interestingly enough, it wasn't the company's shipping services that sent the stock flying Thursday. Nordic American Tankers owns about a quarter of an offshore drilling company called Nordic American Offshore, and the latter just added six vessels to its fleet. While that might not sound like much, this is, after all, a $730-million, Bermuda-based company, and vessels supporting offshore drilling can command daily contract rates that amount to what some Americans make in an entire year.