Philip Fisher was an investor who began his career in the early 1930s. He is remembered as being one of the greatest investors of all time and he helped teach a young Warren Buffett. He is famous for his fifteen points to finding stocks. He is one of the founders of value investing, finding undervalued stocks and holding them for long periods of time.
One of his most famous quotes came about when he was approached and questioned on when the right time to sell a stock was. His simple reply was "almost never."