A journal that only records win or loss and the dollar amount misses almost everything useful. The metrics that actually change how you trade going forward require a bit more structure than that.
1. Expectancy, not win rate
Win rate in isolation is close to meaningless without knowing the average size of wins versus losses. A strategy winning 40% of the time with wins three times the size of losses is substantially more profitable than one winning 70% of the time with losses three times the size of wins. Tracking expectancy (average win times win rate, minus average loss times loss rate) gives the real picture.
2. Plan adherence, separate from outcome
Recording whether each trade followed your predetermined entry, stop, and target rules, independent of whether it won or lost, is what separates a losing trade that was normal strategy variance from one caused by abandoning the plan under pressure. Without this field, both look identical in a journal that only tracks profit and loss.
3. Session and time-of-day breakdowns
Many traders discover, once they actually track it, that a disproportionate share of their losses cluster around a specific session or time, often the period they're most fatigued or distracted. That's an actionable finding a simple win/loss log would never surface.