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 !!
The next step is to buy eth if you have extra fiat. Then sit back and relax. Also I think the falling of price of eth is a good sign for investors to have a good buy entry point in preparation for the coming staking.