Don't be like all the fools who bought high in December, and no doubt have now sold low. Buy now and don't start selling till it's at the $19k highs.
you can not call some long term investor who is buying bitcoin every now and then to store more and more of his money in bitcoin a "fool" just because YOU are focusing on the short term fluctuations. of course everyone wants to always buy the cheapest possible but that is not how real world works.
the only thing you can say is that people shouldn't sell way too late after a big price drop happened and price reached the bottom, that's all.