Think of it like this: the cycles of bitcoin where a bull run leads to a bear run will eventually end. You can already see it happening as in 2017you had an over 2000% bull run followed by an 85% bear market, but in 2023 you barely had a 350% bull run and a much weaker correction. At some point this is going to stop, so by "milking" the bull market you're decreasing your future gains.

What if bitcoin corrects 20% this time, you sell everything on the way to the top, won't buy back on the way down and the run up resumes, leaving you behind? You'll milk yourself, or other bulls milk you and leave you behind.