Based on your financial expertise, provide your response or viewpoint on the given financial question or topic. The response format is open.

Why are some long term investors so concerned about their entry price?
Because buying at discount provides a considerable safety of margin -- it increases the likelihood of profiting. The margin serves to cushion future adverse price movement. Why is so much effort made to get a small percentage off an   investment, if one is then willing to let the investment drop another   20% or more with the reason of being in it for the long term? Nobody can predict the stock price. Now if a long term investor happens to buy some stocks and the market crashes the next day, he could afford to wait for the stock prices to bounce back. Why should he sells immediately to incur a definite loss, should he has confidence in the underlying companies to recover eventually? One can choose to buy wisely, but the market fluctuation is out of his/her control. Wouldn't you agree that he/she should spend much efforts on something that can be controlled?