During the last week I bought coins and they almost immediately fell by 10-15%, and today early in the morning I saw how they fell by another 15-20%. How long will it last?., and whether I should sell for what I have. I wouldn't want to be left with empty pockets. 
For the, the best thing to do is to hold your coin while the price of it doesn't satisfy you at all. In holding a coin, you will literally lose nothing, unlike solding the coin even if the market is red, you will lose big amount of money and will lose profit in the coin that you have.