People investing in the markets typically sell when the price is low, during or at the end of a notable decline, out of panic. And they may buy at the highest price, once they discover a new investment they hear of from their friends, who heard it from their friends, and so on. Or they buy when the markets are reported by various media outlets to be at their all-time high. By the time the news reaches you, it is probably long past the time to have invested.