Waiting for a higher price is good idea for some holders ,but if you feel that bitcoin price is in danger or it starts to go down ,then basically you must sell it before it will go down deep.
No, that is panic selling and that is the fastest way to lose money, sell when you get a profit and if you are in the red, then wait until you are not, the price of bitcoin always recovers relatively fast.
Never do stupid decision when selling, your lack of trust will lead you to losses. You but bitcoin because you believe overtime the value will rise then you should believe on that, we have already seen it many times that every time there's a crisis, whales just consider this as an opportunity to buy cheap bitcoins. If they are successful doing it, we should be doing it also, in the end, if we hold longer, we can rip the fruits of our labor.