I wouldn't recommend to sell all your Bitcoins at this time because the price is still rising and growing more popular everyday.
Unless you really need the money then I would say to sell everything otherwise don't do it.
Why do so many people focus on selling all their coins at once while they can just sell a small portion of their coins? That would make a whole lot more sense as you'll be able to benefit from each market movement. UP - you get to benefit as your other coins gained value. DOWN - you get to benefit in the way that you can buy back more coins for the same amount of fiat. Same basically goes up when it comes to buying -- never buy with all your funds at once.
I think it is because most people trade without opening a trading book, probably one of the first thing you will find in any book about trading is that we should not invest more than 5 to 10 % per trade, this limits the earnings but also limits the losses, but people prefer to buy or sell all their coins at once to try to get more profits without realizing they are increasing their risk significantly.
If a person lends itself to panic, then he does not do very wise things. Therefore, if the price goes down, some people think that bitcoin is dying, and therefore sell all their stocks