It is never a good thing to sell all your coins at once if you because there is always a chance that the price is going to still rise.
If you have then sold everything then you just missed out on some money.
I agree to to only sell some of your Bitcoin and only sell them all at once if you know that this is going to be your last time on Bitcoin.
If not it is allot better to always have some Bitcoin saved up.
Yeah and I think if you have saved bitcoins then you always have an chance to make profits in future when price will go higher so its good to sell them in installments instead of selling them at once.