They trade too often and even when Bitcoin volatility is not high and they get familiar with low volatility as their normal standard. With this feeling, when Bitcoin suddenly to rise sharply, they will sell low and buy high. This trading style will cause them loss of their bitcoin and it's not what they intend to do initially.
I would like to say, they should trade less, hold longer.
I think maybe many of us have thought about this and even tried it, and I am one of them. But to be honest, it was not as easy as we thought, and as a result our bitcoins decreased instead of increasing as expected. So I think holding and trying to find income from work sources, and then applying the DCA strategy is the best way to increase the number of bitcoins. Trading is never as easy as we think, if it really was that easy it wouldn't be our turn to do it.