I find that many people have a habit of holding ETH, BTC, altcoin for a long time and always hoping that it will rise again. If you are a trader, you will lose money for that. Set small target and sell them when you see profits. I only need 3-5% profit when trading.
If you see the market going down, stop loss before it's too late. You may lose 5-10% of the capital but when the market goes down you can buy more btc, eth when you hold btc, eth, altcoin.
Sell all ETH, BTC into Stable Coin when the market goes down
Good advise and yes, when the market is going down, it's much advised to exchange any altcoin to USDT which is stable coin. Then when other coin values goes down, buy it with Tether.
As you said yes, set a minimum threshold of profits from 5 to 10 percent. Though it takes time and energy, it's much advised to do so. You need to be much patient.