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
This is very interesting and good theory also as i follow maximum of your theory earlier. But problem is you said to buy stable coin when market goes down. How you will select stable coin in dull market. Otherwise trading is the best method i think always.