Is it really a big mistake to sell portion of your bitcoin and then rebuy back when the price has dip?
The reason why am asking this question is because with the right approach I think this can also be done and even help you get good value of bitcoin when the price dip but there are conditions that would prompt you to actually sell some fraction of your investment.
It may not be a big mistake but of what difference are you who claims to be a bitcoin investment holder from the retail trader who only buys at dip price waiting to sell when price rise. Are you selling due to emergency (then you are meant to have an emergency funds) or you selling cause there is a price?
That the particular approach is appealing to you it can still be not the right approach towards your bitcoin investment when you have to sell a portion of your holdings at every bitcoin price rise to rebuy when it dips. Do you not think you are investing without a proper duration on your investment? You are holding for 6 or 8 years let it be so as planned.