Everyone has their own strategy for trading. Those who only follow FOMO usually only want to get a little profit to avoid high risks. Buying coins when it goes down is quite risky, because not all coins will easily going up. The team needed "a big news" to attract investors to buy their coins on the exchange, and of course it isn't easy. I think buying coins when it's going up is better, because you only need to pay attention to the moment "buy/sell" to make a profit.