the following rule is always valid: buy low, sell high. Well, how do we know when it's low or high?
It's low after a bunch of scared peoplel literally throw away they coins (remember BTC @ 20k?
It's high when the BTC you bought at 1000 or 3000 USD are @ 20k but you're greedy & want more, that's time to sell (however most of you do not do it  )

Absolutely nothing, rule No. 1 is "do not panic".
On top of it, it's Christmas, people ran out of money & need to sell whatever they have to buy presents

I suggest to buy a good bottle of wine when the BTC is still high and drink it as soon as it starts to crash, eventually no-one can do anything about it, but it's not too painful whatching it fall 
anyone agrees with me?

For some it is, for others (like me) it isn't.
stay cool and do not be afraid to be broke  

bitcoin will live on, if you're not patient you might consider giving up coffee