Buy more if you have funds or if you do not have anymore then better cut loss early and wait for some time to buy lower. When the price falls especially the price of altcoins, it falls deeply than bitcoin that's why I prefer to cut loss because I have seen before when some of my coins lose sometimes 90% of its value. Besides that, when a coin falls 50%, it has to double in value so that you can break even so its better to cut loss earlier.