Anyone taking profit from his bitcoin investment with the idea of buying back when the bitcoin price dumps is taking a great risk because that person will not be patient enough to wait for the bitcoin price to dump so that he or she can buy back his bitcoin because the bitcoin price keeps going high. FOMO will make that person buy back his bitcoin, even with the profit the person took from his bitcoin investment, just to be among those who are holding bitcoin in case bitcoin does the unbelievable. The person will be buying back less of the quantity of bitcoin he or she sold out because of the high price of bitcoin.
It depends on the goal the person had previously set out to achieve in his investment and the strategy he his working with. For someone that had been holding for a long time and had a lump sum of Bitcoin within that period that places him on a good profit, it's not wrong if he chooses to sell part of his holding and maybe reinvest it when the Bitcoin price dumps. For some, it's even a strategy that works well for them and it enables them to effectively HOLD for longer periods of time. It's only bad when you're just starting your investment journey and you're yet to accumulate a reasonable amount and because of a sudden pump in price, you feel its the right time to start selling.
As long as you know what you're doing and you're matured enough to stick with the right strategy that's working for you, continuous holding or choosing to sell when the need arise and buying at your convenience is totally up to you and as long as it's working for you then you're on the right track. The whole essence of accumulating using the DCA method or or buying in lump are all strategies that had been used and is still being used and proven to have help in the course of effective Bitcoin accumulation that will be profitable and whatever method you choose to stick with at the end of the day, as long as it gives you the peace of mind to accumilate at your own pace, just stick with it.