Why do people sell their Bitcoin due to fear of the  current drop in price. Do They feel the price will drop further and never go up again ?

I feel before anyone invests on Bitcoin they should get a proper understanding of how the Bitcoin market operates. Because if an individual has good understanding they will know that the rise and fall in price of Bitcoin is normal so there won't be a need to panic rather see it as an opportunity to accumulate as much as possible in anticipation for a rise in price.