Yes the big and long bearish season just like in 2018 can be happen again after bull season, and hard to predict when is coming. Just prepare for that situation because the market will never bullish all the times. Just take profit and withdraw in to fiat, and avoid all in crypto in this situation. But bull market also have high probability to start again, withdraw half balance in to fiat and another remaining hold in crypto for a few month, so we will not missing if bull market extend.
What do you really want to suggest? because the bear market and bull market have happened very often and often seem very big every three years, but I only see people who make profits with the results of being patient, because in 2018 there are also optimistic people buying some Altcoins and Bitcoins to hold on to in the long run, and the results have been very visible at the beginning of this year, so your advice is not wrong, but it will not apply to those with extra patience.