ability to sometimes gain more than $1k within days.
You should always look at the percentage of the price changes not their amount. $1000 rise at this point is about 5% rise which is the smallest rise that bitcoin usually has. It is equivalent of price going up $50 back in 2016 when price was near $1000.
It had always retraced anytime it reaches $19K plus.
It is because $20k is the highest record price that bitcoin has reached so far and it was the peak of the bubble by the end of 2017 so today it has turned into an arbitrary but strong resistance. Just like all the previous bubble ATHs that turned into resistances before they were broken.