Some big guys can affect on it, when the new buyer comes and buys alot of btc for instance, price can go up, also, there is many things, like on the end of the year market goes up, coz ppl like to spend money, after the january there is always a silent time, even in the regular shop isn't?
Yes at the first half of the year I also noticed that the market becomes silent and after the month of June the price of bitcoin start to increase. It is only a slight drop in the price and will not be a permanent and will last sooner within a day or two and after that the price of bitcoin will again start to increase.
When a rise start now then it will continue till the end of the year which will adopt much higher value in the end.
A huge selling can kill a relatively unknown coin, but not Bitcoin with its over 5 billion USD current daily trading volume. Too much people trust BTC already to let it die so easily. Whenever price goes down big time, there are a lot of buyers appear and the price start rising again. Of course it's easier for the whales to buy coins when it looks like "the end is nigh" because they know for sure that there will be no end. Regular people continue panic selling and end up partially losing their investments, always regretting not holding some time later.
Basically when you panic sell during a bloodbath, you sell your coins to the whales, who are more than happy to collect more of them at cheap price.