I prefer those who sell bitcoin because their original intention was only to take advantage of a short rise, rather than those who panic because some people say that bitcoin might touch a price lower than the lowest price bitcoin reached some time ago. I have seen some of them saying that bitcoin will hit 12k or lower, like you said, so they decided to sell their bitcoin because they want to get the lowest price. Not wrong, but if we prepare from the beginning for that possibility, we don't have to sell bitcoin quickly, because of course with careful preparation we will be prepared to buy back bitcoin at the lowest price. Most people like that are not committed to what they planned at the beginning.
Yes, each person has to choose their own path, and the reasons for the sales might NOT always be the same in terms of how much they actually know about bitcoin or how much commitment that they have in regards to bitcoin as a long term investment, so sometimes they will create various entrance and exit strategies (price points), so they might not even be panicking in regards to carrying out their plan.. but they still might not be as informed about bitcoin as they believe that they are...
and I am not even suggesting that any of us really know where the BTC price is going to go, even though at the same time, it seems to me to be better to prepare for considerable upside scenarios, even if we might not believe the BTC price to go there.
I recall during my first experienced bull run in 2017, I had a relatively conservative plan in which I had considered that the BTC price might top off in the ball park of $3k to $5k, but at the same time I was somewhat prepared for higher price scenarios including that it ended up going up to $19,666, and probably I had ONLY sold around 10% of my total BTC stash at various points all the way up... and I suppose at the same time, I was still learning how to manage my BTC holdings and at the same time the psychology of having the BTC price go up around 5x higher than the more bullish scenarios that I had in mind, but then come crashing back down to the $3k to $5k and then largely correcting back down to around $3k to $5k and maybe mostly staying a bit higher between $5k and $10k for the next three-ish years (between early 2018 and late 2020).
Those are not necessarily easy roller coasters to see the value of your BTC holdings to go up around 78x from the $250 bottom in 2015 and then to come back down to the place that you were considering to be the high range for that cycle.. so there can be some trauma and even difficulties to figure out how to manage your BTC holdings in such a way that is comfortable with your own psychology and even to have enough conviction about your ongoing holdings of BTC to mostly just continue to hold what you have and not to go too crazy in terms of selling any of it.. even if it might well have average costs that are less than $1k per BTC, so the profits still remain pretty decent, whether adding more BTC to the stash or just not doing anything or perhaps even selling a bit of it for whatever expenses might come up.. but if you manage your cashflow well, there might NOT be any need to sell large amounts of your BTC during the dipping times of the BTC cycle.
If we look at all of the investments that we have we might consider if there might be times in we might want to sell some of our BTC so that we are NOT overly exposed to BTC in terms of either how much value we have into it or even how much psychology that we have in terms of having the amount of value into BTC that we have... so sometimes there might be some needs to pull some value out, in the event that we don't have other investments, but if we already have various other investments, it might not hurt to continue to allow our best performing assets (BTC in this cases) to just continue to ride, even if it might be disproportionately overvalued in terms of what had been our original accumulation targets.
In my own case, I had not really known what my BTC accumulation target was going to be, but after I spent about a year (in 2014) accumulating BTC, I started to figure out that BTC was becoming around 10% of the value of my overall quasi-liquid investment portfolio, and I thought that 10% was a decently good target - however, with BTC prices staying flat throughout 2015, I continued to buy and ended up reaching around a 13.5% allocation by the end of 2015, and since BTC prices went up during 2016 and 2017, my allocation ended up growing from 13.5% to around 75% based on BTC price appreciation, and so then it dipped back down to be around 45% and then currently is maybe in the 85% or so territory based on price appreciation..
...so it may or may not be necessary to reallocate, but at the same time we have to remember that if we get out of BTC, then we may well be getting into inferior asset classes, and it may not necessarily be a good idea to diversify out of a winning performer, even something like BTC.. even if our allocation in BTC might have had gotten to be a way higher portion than our initial allocation amount and in my case the amount was 10%, but then I ended up slipping and making it 13.5% or so, and so there would be a lot of sales of BTC even if I were to bring it back down to 25%,,, and I am not even sure if that would be necessary to diversify out of BTC and end up buying something that is likely inferior.