Yes, bitcoin has plummeted about -14,000 $ so far since Dec 2017, and the cryptocurrency market is a mess overall!
In mid 2017, as bitcoin started to skyrocket, we all felt jealous, and most of us who started trading cryptocurrency, just to become filthy rich ASAP, without having any experience or education about bitcoin (or other currencies, or how the stock market works).
Similarly, today, dow jones plunged about 1,500 points, which scared the shit out of everyone; but the cryptocurrency market is much more volatile than stock market, but at the end of the day, these ups and downs are normal.
Everything that goes up, must fall.
Every now and then, bitcoin takes a dip and after that it skyrockets insainly (every year such scenario happens).
Anyway, the main goal of crypto is to make our lives easier, making money transfer faster and more secure, and it opened doors to new innovations like smart contracts.
When hundreds and thousands of users convert their bitcoins to USD, Euro or any other currency (maybe because they want cash, or are afraid of it plummeting), that is equivalent to saying that they pulled out a big supply of money from the market, which eventually will cause the bitcoin price to drop like this.
Bitcoin and other cryptocurrencies are made on top a technology called blockchain, which is here to stay. Just like when the internet appeared, thousands of companies were started in order to invest in this new technology. About 80% of those companies closed, and only 20% survived. Similarly, blockchain started a revolution that everyone is trying their best to invest and take advantage of. Eventually only a few will survive this hype.
So, hodl on and be patient, and believe in this amazing technology.