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 !!
Many large ICOs collected ETH at the price of $500-1500. Now the price is from -x2 to -x7. That's why to save anything projects sell a part of ETH at downfalls. That's one of the reasons for the further falling.