There have been lots of down days with the entire crypto currency asset class. According to Coinmarketcap, approximately 5 are only profitable. Is it possible just to focus on these? Sure since they are profitable. If you saw my post from yesterday, you know you can day trade the crypto currency according to Investing.com. I verified the profitable ones today with either strong buy or buy. These do vary widely including the daytime period as well....

http://quantlabs.net/blog/2018/07/cryptocurrency-day-try-day-trading-strategy/