The trader who checks his P&L 20 times a day may know less about his performance than the trader who checks it once. Because P&L answers only one question What happened to the money? It doesn’t tell you whether the money was earned through a repeatable process. Consider two traders. Trader A makes $8,000 this month. Trader B makes $3,000. At first glance, A looks better. Now change the information. Trader A took 42 trades, doubled his normal position size after a losing streak, and made most of the month’s profit from two unusually large winners. Trader B took 18 trades, stayed within his normal risk parameters, and produced almost the same results across different market conditions. Who had the better month? The answer changes once you measure something other than the account balance. That’s the problem with performance measurement in trading. The most visible number isn’t necessarily the most informative number. A brokerage statement can tell you what your decisions produced. It can’t tell you whether you should trust those decisions again. That requires a different record. Not just How much did I make? But What kind of trader did those results require me to become?