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.
It is good to invest with projects that are worth more in development and market price. Some meme coin might become left behind if the market continue it bull run. Shit coins might have a serious fall if the market become instable having much loses when other coins are still doing well with there price movement.