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.
Buy now and sell after a year or two is not an investment plan but a gamble. There is no reason for the price to rise * this week * so we may see further declines.
If you want to think rationally, you'll see how the market looks and what will happen in the coming days and then decide to buy, sell or wait longer.
Personally, I expect to see stability or further declines in the coming days "a week or two" after which we will see a longer period of ups or downs.