Imagine having one bitcoin.
You sell that bitcoin at the current price(around 3800 USD).
Bitcoin crashes again somewhere around Christmass and the price goes down to 1K USD.
You buy 3.8 bitcoins with the dollars you got from the previous sale and you HODL.
In 2019-2020 bitcoin recovers to 10K USD (or maybe reaches 20K ATH).
You have made atleast 38K USD.

I know it's not guaranteed to happen,but hey,this is the Speculation forum,so why not speculate about this.
I think that this is every crypto whale's trading plan for the next 2 years.
It's definitely the basic idea buy now when the price is low. We know already rhe the power of BTC and many are becoming unexpectedly to be millionaire due to this kind of business. What is required about this is that we should have a strong emotions to hold such pressure when timea get rough.