Actually Before I comment on HODL or no HODL, I need to say it depends how you purchased the coin and at what price.
Suppose I purchase something at $100, it means I am confident on my research that its price is $100, if now market start trading at 90$ and my research still says it is good at $100, then I will HOLD. If I now come to some new facts that make me believe that it actual price $80. then I will sell at $90 at once.
Bitcoin price is unstable and no one knows when it will rise. If you are an investor you have some goal that you want to achieve like in profit. If the price doesnt get the profit you want then you probably need to hold it. It can also avoid you from losing money. Holding is one of best strategy we can use while bitcoin is still recovering.