a few days ago ethereum experienced a drastic decline. and it turns out it's currently under $ 200! My personal predictions are wrong, and may not be true. what's the next step?

I think vacationing is a good idea while enjoying a vacation !!
Yes it's better to take a vacation because market is not good for the holder , but don't panic just hold your coins and take a vacation , and to those who have no alcoin in you wallet , don' t you worry because price is very low so it is good if you buy altcoin .