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.
In my case i do not invest on not so popular coins thats why if market will go red like what is happening right now, my short time trades will become long term trading. I did not invest in not so popular coins that has a chance to to be vanish.