About 50% is usually the normal negative take on sell offs and I would say any push past that to lower prices is more obviously a time to buy with less hesitation as it relates better to long term prospects even if you had to wait years it wouldnt be totally wrong. Obviously more examination of the chart at that time vs other measures such as FIAT, interest rates, inflation and any other competing standards.
Right now price is descending below a
2 day average price, it has lost momentum for the moment which is a large part of the fastest gains. That can just mean we need to revise lower prices, reset this momentum to steady price expectations then start over and thats happened a few times already this year. Most obvious underlining to YTD lows has been 50 day average I think, I've heard others mention 20 EMA also.
It "could" happen, remember we became 3k from 20k before, the half is 10k, but usually that hurts alts more than it hurts btc, why? Because even though we became 3k, we recovered from that quickly, became around 6k for a very long time, then became around 7k-9k for a very long time, that is not good of course because we were around 20k at one time and now we were around 7-9 and moving in between those numbers so that was bad.
However the second largest crypto in the world was ETH and it dropped from nearly 1500 dollars to as low as 88 dollars at one point, that is around 95% fall, can you imagine bitcoin falling 95% right now? That would make 64k all time high drop 95% and be 3200 dollars right now. That is seriously bad, we wouldn't want that right? But if eth drops it could still become 100 dollars and that is the trouble for people, they are not afraid of their bitcoins (maybe some do) but I am mostly afraid of my alts.