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.

The Dow Jones Industrial Average (^DJI -0.12%) had its worst day in a month today, falling 153 points, or 1%, while the S&P 500 and Nasdaq dropped 1.4% and 1.9%, respectively. As we've seen in the past, positive economic news seemed to send investors running out of fear of the Fed. Third-quarter gross domestic product was well ahead of expectations of 1.9% growth, coming in at 2.8%, and earlier this morning the European Central Bank cut borrowing rates to a new low of 0.25% to fight deflation and help the weak continental economy. Both items should be bullish for stocks, but investors are worried that the Federal Reserve will begin tapering its bond-buying program if the economy shows significant improvement. Tomorrow's jobs report should be the best indicator yet of the Fed's next move.

Twitter (TWTR) stole headlines, jumping 73% in its debut to close the day with a market value of $24.5 billion. Shares are priced highly as the company has yet to turn a profit and the stock sports a price-to-sales ratio of 26.5. Still, that is not far off from Web 2.0 peers such as LinkedIn and Facebook, and I'd expect Twitter to make a more concerted push toward profitability, like Facebook did, now that it's a publicly traded company.

Whole Foods (WFM), meanwhile, dropped 11%, after providing weak guidance in its quarterly report. The gourmet grocery chain said it now expects to grow sales 11%-13% this year, a percentage point below its previous forecast, due rising competition and a general downward trend in retail spending. Co-CEO John Mackey also said, "The broader economic environment seems to be impacting our ability to attract new customers at the same rate." Same-store sales in the quarter still grew strongly at 5.9%, and earnings per share of $0.32 beat estimates by a penny. Still, the company seems to be running out of "low-hanging fruit" for new markets, and has been discounting and introducing value brands to appeal to a wider range of consumer.

Finally, Disney (DIS -0.83%) shares fell 2.7% in regular trading and another 1.7% after hours once the entertainment giant reported earnings. Earnings per share of $0.77 beat estimates by a penny, while revenue grew 7% to $11.57 billion, topping the consensus at $11.4 billion. Shares seemed to drop because of a 1% decline at its pay TV unit (including ESPN) but that was largely due to payments from cable providers, which came earlier than normal. Sales at theme parks and in its merchandise segment also grew respectably, and Disney said it will release the next Star Wars movie on Dec. 18, 2015. Despite the modest drop in share price, this was a solid report for Disney.