Everyone who conducts crypto trading must already have principles and know about profit or loss. My principle is that I will never sell when I see the results will lose, I better hold when the coins that I have bought are decreasing in price (holding is not afraid of losses) but part of the strategy. And I will sell when I increase, although I will definitely sell a little. Never be afraid to experience a loss, because loss is one of the risks in trading. But you must have a strategy.
When it comes to holding, you really have to handle this with great wisdom, because there are some coins that maybe going down after they surge, and if you are not fast enough to join the group of people selling at that time, you may never ever get the chance to do so again because such coin may never rise, just like some of the coins majority of us all fail to withdraw in the last altcoins bull run, look at what they have all become now, imagine we had taken step to sell them off then, would there be any of the regrets we are having now? Holding is better for any coin you can confidently rely on like Bitcoin, that no matter the fall, it will always come back on its feet.