Hindsight bias is the tendency, after an outcome is known, to see it as having been predictable all along. In trading, it makes yesterday's chart look obvious and corrupts the lessons you take from your own history.

The obvious-in-reverse chart

Looking back, the top and bottom are marked and the trend is clean — so it feels like you should have caught it. But in real time, that same chart was a wall of uncertainty with equally plausible paths (why prediction is hard). Confusing the clarity of hindsight with the fog of the live moment breeds unfair self-criticism and false confidence in equal measure.

How it corrupts your review

Hindsight bias poisons the most valuable habit you have — reviewing your trades (keeping a journal). "I knew that was a loser" rewrites a reasonable decision as an obvious mistake, or a lucky win as a brilliant read (process over outcome). You end up learning the wrong lessons from a story your memory edited.

Nothing is obvious until it's over. The chart that looks like a gift in hindsight was a coin toss in real time — grade the decision you made, not the one hindsight wishes you had.

Reviewing honestly

Record your reasoning before outcomes are known, so your review compares the real-time decision — not a rewritten one — against what happened (reading your equity curve). Judge whether the decision was sound given what you knew, not whether it worked (consistency over being right). A mechanical system sidesteps the whole trap — its rules and every fill are logged objectively, immune to a memory that edits the past (mechanical vs discretionary).