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.
I think the strategy of buying low and selling it high only for the new traders not for professional trader .At the end they are always in loss if nothing exceptional happen on the invested coin .It can be profitable if you choose the top coin you can make profit in most of the time if market go through with the positive trend .I never suggest on this way of investment or trade i wanna suggest research both fundamental and technical analysis before enter the market if you don't know how to analyse do study on it .