HODLing is not as simple as just buying and keeping it for the long term. You still need to stay aware of market movements and be ready to make the sell if the timing is right. Doing nothing is not an all encompassing strategy, but can be useful at times as long as it is just part of the overall strategy. Not acting could cause you to miss out on some great selling or buying opportunities, either to cash a profit or to increase your holding in a particular coin.