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.
At this situation you must control your self in panicking don't sell immediately as what you see the cart was moving down the price of bitcoin. Its just a part of crypto currency and bitcoin is the one, because it is volatile the price was moving like what up and down. Therefore don't be panic or quick sell your bitcoin because of going down price you should not follow your emotion.
Timing is need of investing or trading bitcoin or if your not maybe it lost your money. Make wisely decision in buying coins to earn more money not turn to wasted money.