I think some western traders already cashed out for Christmas sooner than previous years lol. BTW, according to what I read, some whales tried to create FUD (Binance office raid, China ban more crypto exchange..etc..) to accumulate more BTC. Besides, some China ponzi organizations sold on Huobi and Okex leading to this severe dump.

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This is normal since the introduction of leverage trading. When you could only sell in anticipation of the dump the market was more stable but now every move can trigger an avalanche of bot sales and liquidated shorts. That fast move up and down looked like a short squeeze attempt.

Somebody wanted to liquidate people so he bought a lot of coins to pump the price but it didn't go very far and he saw that and sold everything he bought minutes earlier.

I'm sure he meant the above and that he was writing the date in the european style, which I'm also not used to.
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You sound like you might have more invested in it than you can afford to lose if these price swings are driving you crazy.  Maybe you should reevaluate how much bitcoin you own so you can keep your sanity, because this past week hasn't been any more crazy than a lot of other times in its history.  Plus, this kind of volatility is going to be a part of bitcoin and altcoins for the foreseeable future.

I wasn't into bitcoin in the early days, but by looking at the chart I can see that those were probably the most insane times imaginable, right up until Mt. Gox crashed.  And I do vividly remember 2017 and how wild the market was then.  It was going up, so everyone was euphoric but it can also go the other way too, and just as fast.

You said it right. Bitcoin may go up or down 20 % in a mater of few hours.