For altcoins, buy low and sell high, and you will make a profit. Although this statement is correct, it does not go for all coins. Some people think that when the market rebounds, their altcoins will rise with it. But the result was leaving the market at a loss.
So choose wisely and follow up the project. See what their developers are doing, or just hiding behind the prevailing saying.
Most altcoins won't recover. People will point out the coins that do, but if you seen the coin graveyard its massive. Go find me all those 2017 masternode coins that survived lol. Millions drained because people say if you don't sell you never lose. Those same people haven't been through a crypto bear. This isn't the stock market.