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.
Yes as we know, if price is fallen its a chance for some trader to buy as much as they can. Most of the trader always hunt for that situation so that trader can minimize there expense.
In orther to buy bitcoin it would better to wait for the time that the value will fall down, so that we can buy it in a cheaper value and a lot we can buy.