A tendency arises among us. When the value of Bitcoin increases a lot, we start trading more. Which puts our trade management in jeopardy, during which most of the time people face loss.
Thats called FOMO and the selling that occurs when bitcoin value drops a lot is the opposite of it. This is common and something you can see during every cycle.
The thing to take advantage of is the high selling price that you can get when the price is at the top and people are FOMO buying, so you can dump on them at a high price and hold that USDT for when the price drops, people will panic sell and you can use the USDT to buy at a discounted price.
So yes trades should be closed/sold when the market is bullish and opened/bought when the market is down.