I don't think selling all bitcoin in the bull market is a good idea. Why? Knowing the fact that the next bull price will still come as bitcoin continues to grow, so I don't think selling all my bitcoin in the bull market is the best.
It depends on everyone's personal investment goals and plans they have always had for their assets. Some might prefer selling all when they see that the price is good and they are getting enough profits as per their plan, and some might only sell a portion and keep some hoping for a higher price or maybe for the next bull run.
Everyone is holdle bitcoin in the bear market and planning to sell in the bull market
That's the basic idea; buy low and sell high. So, when the market is down, people tend to buy, and when the market goes back up, they tend to sell to get a profit and repeat the same in the next cycle.
when finally, the bull market comes should I sell all my bitcoins and prepare to accumulate from afresh in the next bear market again? or should I keep some percentage to continue the accumulation?
Again, it depends on what you have always had in mind. Everyone will have a different plan. If you ask about me, I prefer selling all in the bull run and then accumulating when the market goes down again because I believe it's better to secure the profits from the previous cycle.