Hodl is the way forward if one really want to make profit from investment. One has to exercise patients hodl. That's is why it's good for one not to use all fund to invest or no source of income, so that when it's dip their won't be panic.
Everyone has a strategy in this regard and what you are saying is also not wrong but as long as there are better and good moments to take advantage of, I think investing in times of decline and selling them now is also a move that is not wrong