Dump more then 10-20% in 1 day in crypto like bitcoin is may cause a fear Because we know much of Bitcoin's pre-history that Bitcoin's price went down a lot from ATH. So it's natural to be scared when such massive dumping takes place. Something like that happened recently. However, those who know the history of Bitcoin also know very well that if Bitcoin is held for a long time, it can give many times more profit, so those who are real holders are not afraid of any situation.
Why be scared then? You know that Bitcoin's only going to go up because presumably you've been through more than one cycle by now. So it makes no sense to panic over your portfolio going down by 10% or 20% unless you've only just heard about bitcoin and bought it yesterday like the guy above you wrote. But even that can be solved by not looking at the price more than once every 12 hours.