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.
For you to have a better chance to earn you would always consider the dumping price if every coin as an opportunity for you to earn because if you will buy coin in terms of the low price yoy could earn in the future regardless the price of Bitcoin when you bought it because Bitcoin price also developing and could put resulting for a more chance of earn and a bigger profit.
When altcoins are falling, I'd prefer selling and buying more bitcoin. Bitcoin should be held long term.