Doing mistake in the process of trading is avoidable if the trader is careful about it. And also I agreed with the statement of irhact, anyone that is trading most not hold because the trader most buy and sell and if the trader must buy and sell then there is no need for him to hold. Trading can not be a long term because it is a daily business. The trader must trade to make profit every day.
Trading can be both short-term and long-term, it is not necessary for a trader to buy and sell every day.
Traders are also different, there are those who like day trading, they make a lot of transactions every day, but there are also those who trade not so actively, they also follow the market, but they make significantly fewer transactions, perhaps only a few transactions per week, or even per month. In addition, there is long-term trading.
And besides, a trader can easily be a holder as well. He splits his funds, part of which goes to hold, and the other part he trades, and this happens very often.