I kept a trading journal for two years and it changed nothing, because I was writing down what happened rather than what I decided. The rewrite took one afternoon and it is the only process change that has held.

Three fields, filled before the entry

• What has to be true for this to work.

• What I will see first if it is not.

• The size that lets me be wrong twice and still be here.

The trick is the tense. A journal written afterwards is a story. A journal written before the entry is a test, and the test either passes or it does not.

What it caught

Within a month it caught the thing I had been doing for years without seeing it: taking the second entry at full size after the first one stopped, on the argument that the level was now better. The level was not better. I was.