some points I would like to add is the greediness in the mind of the investor. Other thing is that he does not know exactly when to sell. The investor must be clear in his mind that after how much profit he should sell the amount
You must need to be greedy if you have invested with only bitcoins. People who invested in bitcoins some 5 to 10 years back and being greedy are making massive amount of profits right now. So, being greedy cannot be a problem especially if you are an investor and you have invested into bitcoins. Investors will lose only when they choose shitcoins and/or not bothering about technical things while investing.