While it would not be a good idea to sell all bitcoins in a bull market, some bitcoins should be kept in the fund. There are many investors who are anxious to see a bull market, and they think that if there is a good profit, they should sell everything. However, the trading strategy may differ from one person to another. I agree it can be a good idea to sell your bitcoins during a bull run, but sell 50% without selling all the bitcoins. Because there is no guarantee when the next bear market will occur. If Bitcoin really go to moon if the price goes above 100k then you can consider it.
That's why we need to have appropriate plans and goals for buying and selling. We should not follow the flow of the market because we will never know where is the bottom and where is the highest peak of the market.
I will sell 50% of my bitcoins when bitcoin reaches its 1st target of $100k, and I will hold the remaining 50% until bitcoin reaches its 2nd target of $150k. If the market then continues to reach a higher ATH, I will accept my profits because I have achieved my target. But if the market suddenly drops later and I can't achieve my second goal, I won't regret it too much because my plan is 50% complete. In investing, everything is very unpredictable so we should have a specific plan, don't invest based on emotions.