If we already have bitcoin, stay calm will be the good thing to do. And if we still didn't have any bitcoin in our wallet then the best way is to wait till the good sign to occur to start to make buy order.
First is to keep calm when prices start to fall, your calmness will make your calculations not messed up, so you can make good choices,
then if your analysis shows prices will rise soon, then it's good to buy, if your analysis price gets worse then holding is best..