People fail in trading because they are not capable to win. Not only because they don’t have what it takes to make a profitable trade, but they are also not well prepared enough to trade due to lack of knowledge and skills, and most probably they lack the trading experiences that will make them master their trading. However, some people fail in trading despite of their trading knowledge and experiences, but since they find it hard to control their emotions, and would always based their decision from their emotions, then this kind of people will never win from their trades.
I'll agree with you more that people fail because they can't control their emotions, some people get too excited when they want to trade and the excitement will cause them to make a wrong call. They'll fail when trading not because they don't know how to trade but because they can't control their emotions. Some traders are falling because they don't time the market perfectly. Just knowing how to trade isn't enough to become successful when trading but you also have to know the perfect time to enter the market. You shouldn't put a sell order when there's a news that's giving Bitcoin or any other cryptocurrency that you're trading a good publicity and also when the publicity is bad you shouldn't be buying that coin or you'll lose from the price of the coin falling.