Sorry to make you panic, I figure while there's a few more days left in 2017 I'd keep the panic train running!
Bitcoin, Bitcoin Cash, Ethereum, and Litecoin are all dropping rapidly. However let's keep in mind the glory of crypto currency is the basic rules of supply and demand.
Since Bitcoin has a finite number for supply, the only factor that can be controlled is demand. We are about to witness a lot of moves by banks to discredit crypto currency as an investment and try to create their own bubble in investments (has anyome seen "The Big Short"?)
So everyone just calm down, the market is taking a dip and it's more than likely due to the holiday/tax season.
No reason to jump ship.