There are two basic things that need to be implemented when the market suddenly falls like yesterday to make a profit. First, the attitude must remain calm by thinking that it will recover. Second, take the opportunity to buy as many coins as possible, such as top 10 coins.
This is very basic, and while important this is not going to help you much on the markets of today, people need to go way beyond that if they are actually thinking on making profits over the short and long term in this market, now I know this is not easy and it is going to take time to develop those skills but it is necessary to do this as whales are now incredibly big and can move the market as they want, especially when it comes to coins outside the top 50, and something like this is not going to be enough to protect you from their maneuvers.