Bitcoin drops because money is switching into Alts and BitcoinCash that was added to Coinbase.
As soon as fomos will lose money, all the money will be moved back to the good old Bitcoin. This will happen any day now.
Currently, there is no fundamental nor a technical analysis related reason for the decline of Bitcoin.
On the contra, the upcoming forks and the especially Segwit2x will draw even more attention to Bitcoin.
This makes 20-25k$ reachable by the end of the year.