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.
Even if such a bearish phase occurs, the long term holders don't have to worry much. Because the prices are going to recover eventually and in all probability a new ATH will be attained. The global adoption of Bitcoin is happening at a rate which was not even imagined before. A couple of years back, if I was telling someone that Bitcoin would become the legal tender of an independent UN member nation, then I would have got labelled as insane and mentally unsound. And yet it has happened. And who knows? We may be only a few years away from Bitcoin becoming a global currency, accepted across the globe.