For me, panic sell is good because the market is cleared of investors who happened to be in the market by accident to make a quick profit. And above all it is a great opportunity to buy coins cheaper. Panic when buying or selling always makes you make mistakes, so to avoid this, you must have a plan.
As we see in the situation with BTC, many holders who have big number of BTC made a big sale before christmas so the price fall. Panic is not our friend now so we need to wait a little bit and in 2019 there will certainly grow.