This assumptions may be due to the fact that some users face lots of losses due to impatience and not wait for the profit. It means that you should think about the profit that if you have profit up to 5% or may be 10% then you should sell that coin as the greed behaviour may be sometimes become the reason of your failure. Whenever the price become in  dip then at least wait for the initial price to rise as selling at low price can make you loss of capital.