Hey there!
A question of panic selling was already discussed on this forum a billion times. But whats bad here? If you are sure that the price will grow back then you can just buy some BTC in better rates. The more dangerous will be the situation when someone is buying BTC while being afraid of loosing some profits despite the fact that pump has already happened (I'm calling it a panic buying). Thats seems like a straight way to lose money and make a bubble.
Actually it's the other way around. Bitcoin panic buying will still make you money even if it's less than what you would make if you buy at the drop, but it will be profitable at the end.
On the other hand BTC panic selling is the stupidest way to lose money, even if bitcoin is a bubble what chances are there that it's going to burst at this certain drop?? why not the next one? or the one after it? or even after getting to 100k$ ten years ahead??? We just can't know.. What we do know that bitcoin had several drops and it recovered from them and most probably any drop we see won't be the last one.. So we just have to HODL and sell BTC only when we need to..