The profit taking between traders and investors is different, but in principle it must have the price target. Before we buy/sell in the market, we must have a careful plan so that we can stay in the market for a long time.
The market is very dynamic. No one in this world can accurately predict the direction of the market. If you are absolutely sure of the prospects of the portfolio you hold, then I don’t recommend selling everything. If you are not sure, it is best to take all profits and mix in a new portfolio that is still promising. The market will always go through a "bearish-sideways-bullish" cycle, so we need to learn to take profit/stop loss.
It is very difficult to find the right time. With cycles like you said no one can predict accurately. Of course people only speculate about the state of the market. I as a trader after studying and analyzing the market and making a decision to trade, I have set a profit target and a loss target. Stop loss can not work with certainty, minimizing losses is a good course of action for me.