As long as you haven't sold your bitcoins, you haven't lost anything, we still have it ahead of us. The rule that I learned for myself - do not buy anything on the bear market.
I agree the main mistake of beginners is to buy at the top when the rate is at its peak , or buy now on the bearish, you need to learn to trade all the people that are associated with the cryptocurrency, and try to buy at the beginning of the bullish movement