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
Traders always take little profits along the way and that is some how quite different from investors. I believe those that are saying we should hold are investors and not traders. Those that buy bitcoin when it was around $560 in November 2016 and did hold since then till December 2017 when bitcoin went as high as $19000 and sold has really make money from the market.