This is the main reason they said market is volatile and anything can happen at any given point but how do you control it as an investors or trader, is to have it parted after securing your profit for the maintime. What i mean is that if you buy a coin worth of 300$ and immediately in pump to 500$ first you sell your of 300$ and take profits leaving your 200$ gambling with. Then if you just buy and market declining what to do is don't panic keep accumulating more and more then you would see that when the market bounces back then you have double of what you had invested earlier.
You will likely do much better if you have some kind of a long term plan in regards to bitcoin, and sure if you cannot resist but to gamble and/or trade with you bitcoin, make sure that you are not gambling/trading with more than 10% of your bitcoin - while at the same time, don't be cheating by continuing to dip into your main stash of bitcoin when you are losing the 10% that you are fucking around with. There are ways to discipline yourself with limits but also to potentially still gamble/trade within such limits.
Usually If is me I would keep accumulating without even selling or having to take any profits knowing too well that we haven't achieved this year ATH.
Any investor who knows about bitcoin and how it works can never rush to sell his bitcoin except for shitcoin that doesn't worth to hold for long period of time and of course those shitcoin can never be added in our portfolios if they don't have any potential, so that is why it's better to only choose bitcoin for long term race than short time projection. Even as that 10% is pretty much okay to be trading with provided he won't go down to much more of the holdings, as most times trading seems to be gradually reducing ones possession.