"We must not think, "Well, we have all the truth, we understand the main pillars of our faith, and we may rest on this knowledge." The truth is an advancing truth, and we must walk in the increasing light."

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The investor is neither smart not richer when he buys in an advancing market and the market continues to rise. That is true even when he cashes in a goodly profit, unless either (a) he is definitely through with buying stocks an unlikely story or (b) he is determined to reinvest only at considerably lower levels. In a continuous program no market profit is fully realized until the later reinvestment has actually taken place, and the true measure of the trading profit is the difference between the previous selling level and the new buying level.

— Benjamin Graham