I think the most common mistakes and problems of the traders are in the patience that sometimes makes them selling their coin too soon. and if they can be patient for a while, I am sure that he can prevent a big loss. the patience is the most thing that we should have and the rest of that list will be following and we can get the profit in the end.
Getting panicked is one of the most common reason which results in the loss of money as this is the time when you get to know how much control you have over your emotions and that if you fail to keep your nerves under your control, then you suffer a huge loss of money. Other than that, lack of knowledge is one more reason because of which the traders experience such situation which then result in loss of money.