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.

Today, the stock market mostly recovered from its poor performance yesterday, with solid retail-sales data and good results on the earnings front from major U.S. banks paving the way for substantial gains of more than 1% for the major broad-market benchmarks. But even amid the cheerful atmosphere, GameStop (GME -6.59%), AmeriGas Partners (APU), and Intercept Pharmaceuticals (ICPT) all found themselves on the losing side of the ledger, with substantial share-price declines on the day.

GameStop plunged 20% after the video game retailer said that its holiday-quarter results couldn't live up to high expectations from investors. Gains in U.S. same-store sales of 7.1% and an even more impressive 17.4% jump in international comps helped revenue climb 9.3%, but sales of new software fell by 22.5%. GameStop also gave negative guidance for the quarter, marking down its earnings range by 6% to 9%. Moreover, with Sony (SONY -2.01%) offering its own digital distribution alternative recently, GameStop will increasingly have to deal with challenges to its business model even as it suffers natural decay now that new consoles from game-makers have come and gone.

AmeriGas Partners fell 5% after the company priced an offering of 8 million partnership units more than 4% below yesterday's closing price for the units. The master limited partnership, which focuses on the propane distribution industry, sold the units on behalf of an affiliate of Energy Transfer Partners (ETP), which had owned 24% of AmeriGas prior to the offering and will own between 14% and 15% following it. The deal represented an exit strategy as part of AmeriGas's acquisition of Energy Transfer Partners' propane business in early 2012.

Intercept Pharmaceuticals dropped for a second straight day, losing 30% as the company said that it might need to enlist the aid of a larger drug-developer in order to maximize the potential success of its liver-disease treatment prospect. At this point, with so far to go before the drug can get approved, let alone marketed, such speculation is only natural -- even if it does lead to wild swings in the stock. For now, though, volatility has become commonplace in the biotech and pharma sector, especially among small development-stage companies with high-profile prospects with promising but uncertain futures.