What I usually do if prices are falling most specially if the coins are very low, I would buy more coins from a much lower price and your total amount of couns would then be divided; the result would be lesser losses. Read or research on google about books or ebooks on trading.
When bitcoin prices are the best opportunity to buy cheaply and buy as much as possible, but they must be studied and predicted to find info through google or something else and all to achieve the perfect or as expected. after buying at a cheap price we have to hold it and wait for bitcoin the price to go up and sell it according to the desired target. it all depends on the plan and strategy for those who use it all its purpose to gain more profit.