The price of cryptocurrencies basically follows the rules of demand and supply. As the coin becomes scares it becomes more valuable and hence the price increases. One common mistake most investors do is that, once they see the price of a coin is going down, they hastily dump what they also holding which increases the supply more than the demand and further reduces the value of that particular coin. Later we try to put the blame on the team that they are not managing the project well. Let's help sustain our coins by avoiding panic selling. Its a collaborative effort.
Agree with you many people are selling their coin when they see the price was falling, and sometimes they blame who handle the ico because the price was cheap and then they will say that the project was scam, the project was dead they didn't even know that they are doing will give to the investor a panic to sell their token that purchase from the ico in result the market was dump.