Holding your coin for a good period of time is important but holding a good coin is more important. But a wish and smart investor will think of selling to rebuy back at a cheaper rate whenever the opportunity present itself.
I would even say the first step to be able to get the best from any investment is knowledge. It is always this knowledge that will guide your decision making and for most part of it, a lot of people who are always in a haste, or very impatient or panic easily are the ones who are just after some means of getting rich fast and they never care to understand what makes the future important, and even if you have to take advantage of some short term movements, you still want to be sure you are doing it right with wisdom.
Being patient is a virtue that comes with the ability to know what you are doing at every certain point in time and that is what is lacking in so many people. When a holder loses his faith on a coin, he get panic and then transferring his wealth to another person who may be another holder but he gets for cheaper prices (by considering current market situation).
As per OP, the current down market conditions trigger the process of transferring wealth from pessimist to new optimists. I am getting this perspective view now only but fortunately I am a long term holder of bitcoin and I never turned as pessimist even at hard times like bitcoin broke $6k levels.