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 stock market appeared ready to end 2013 on a whimper rather than a bang, with Monday featuring mixed moves among the most popular market measures and relatively little volume. But that didn't keep certain stocks from posting sizable moves downward, with DryShips (NASDAQ:DRYS), Myriad Genetics (NASDAQ:MYGN), and Direxion Daily Gold Miners Bull 3x (NYSEMKT:NUGT) among the worst performers in Monday's market.

DryShips fell more than 6%, giving back just a portion of the shipping giant's 27% gains last week. Several analysts over the weekend pointed to those gains as a golden opportunity to take profits, even as others believe that the worst for the shipping industry might finally have passed. With exposure to both dry-bulk and tanker shipping as well as its interest in its Ocean Rig (NASDAQ:ORIG) deepwater drilling affiliate, DryShips offers attractive diversification for those looking to avoid a pure play on any one of those subsectors in shipping.

Myriad Genetics dropped 14% after investors panicked about possible reductions in reimbursement rates from the Centers for Medicare and Medicaid Services for its genetic tests. The proposed reimbursement rate from CMMS would lop nearly 50% off the current figure that Myriad receives for its test. Even though some investors argued that prospective cuts were already anticipated and that Medicare represents a relatively small part of Myriad's business, shareholders didn't hesitate to dump their shares. Myriad will now have to hope for the same sort of reimbursement reversal that has happened in previous years to other companies that rely on Medicare.

The Direxion Daily Gold Miners Bull 3x dropped 8%, as the triple-leveraged ETF followed gold-mining stocks downward in a late-afternoon drop as gold prices fell below the $1,200 mark. With many predicting that the price of gold in 2014 could remain weak, miners continue to find themselves under fire as cash flow becomes an increasing concern. Even major miner Goldcorp (NYSE:GG) fell more than 3% today, and prospects for smaller miners are looking even grimmer in many cases.

Fool contributor Dan Caplinger has no position in any stocks mentioned. You can follow him on Twitter: @DanCaplinger. The Motley Fool has no position in any of the stocks mentioned. Try any of our Foolish newsletter services free for 30 days. We Fools don't all hold the same opinions, but we all believe that considering a diverse range of insights makes us better investors. The Motley Fool has a disclosure policy.