I would like to understand the main reason behind the bitcoin dip/crash (whatever it may be). Currently BTC is trading at 12.5K on preev.com, and I am beginning to become scared as to what the near future may hold for bitcoin.

Is this a Bitcoin crash? Or is it a crypto crash too? Is it just the holiday season or something else? We can also see on coinmarketcap.com that in essence, almost ALL alt-coins are also down by a similar amount in %.

Hold or sell, what do you think?

PS: Please don't just spam this thread with:"Sell now, it will crash" or "Don't worry, it will go up". Base your points on facts that drive the discussion forward, not just general terms that have been already written down many times before.