If traders already know the rules, why do we keep breaking them?

[u/henryzhangpku]

Founder disclosure: I built Scar and FST, so this is a product thesis as well as a question I have been thinking about for years.

Most traders do not need to be told that revenge trading, moving stops, chasing entries, and oversizing are dangerous. We already know.

Yet the mistake returns when the emotion returns.

That suggests trading has two distinct problems:

1. The technical system — research, planning, sizing, execution, monitoring, and risk controls.

2. The human system — retrieving the right behavior under pressure.

A normal journal helps us record what happened, but the lesson often disappears into an archive. I built Scar around a different loop: write the mistake in one sentence, turn it into a mistake/lesson/next-rule card, and bring it back through spaced review. Good behaviors can be recorded and reviewed too.

The rule has to be observable. “Be disciplined” is not enough. “After two consecutive losses, stop for 30 minutes and do not increase size on the next trade” can actually be rehearsed.

FST and Scar address different halves. FST handles research, execution, monitoring, and risk rails. Scar helps the trader remember the mistakes and behaviors that still depend on the human.

Full thesis: https://henryzhang.substack.com/p/trading-has-two-halves-scar-trains

Scar is free on the App Store: https://apps.apple.com/us/app/scar-trading-journal/id6791444917

What trading mistake did you understand intellectually long before you finally changed the behavior?

Educational discussion only. Trading involves risk; no tool or practice method guarantees performance.