Risk and position size · Chapter 5 of 6

The daily limit and the stop-trading rule

Q: What makes a daily limit actually work?

Deciding it in advance and treating it as mechanical — A limit evaluated in the moment is evaluated by exactly the state it exists to control.

Foundation6 min read · part of Risk and position size

Per-trade risk controls one outcome. It does nothing about the sequence, and the sequence is where the real damage happens: the third trade taken because the second one lost, the sixth because the fifth nearly worked. A daily loss limit is the only mechanism that reliably ends that, because it removes the decision from the person least able to make it.

A workable limit is usually two to three times the per-trade risk. At one per cent per trade that means stopping after roughly a three per cent day. Set it much tighter and normal variance ends your sessions; set it much looser and it stops being a constraint on the day it matters.

It only works if it is mechanical. A limit you evaluate when you reach it is not a limit, and the evaluation always resolves the same way, because the state that produced the losses is the state doing the evaluating. Write the number down, and treat hitting it as the end of the session in the same way a closed market is the end of the session.

There is a second limit worth having, and almost nobody has it: a maximum number of trades. Loss limits do not catch the day where you take eleven trades, finish flat, and have simply been gambling with a working method. Frequency is a behaviour in its own right, and a cap on it is the cheapest guardrail there is.

Both limits belong in the plan alongside position size, and both are countable afterwards. Being able to say "I broke my daily limit twice this month" is a far more actionable sentence than "I need more discipline", because the first one has a number that can go down.

What to take away

Per-trade risk controls one outcome; a daily limit controls the sequence.
Two to three times the per-trade risk is a workable daily limit.
A trade-count cap catches the flat-but-reckless day a loss limit misses.

Where it goes wrong

Treating the limit as a suggestion to be evaluated when reached.
Setting the limit so tight that ordinary variance ends every session.
Having a loss limit but no frequency limit.

This chapter, measured against your own trades

In the app the same chapter ends in your figures rather than an example: how often you did the thing it describes, over your last ninety days. You pick one change to make, and Evidence checks afterwards whether it actually changed — from your journal, arithmetic, no opinion involved. Questions you get wrong come back a week later and again a month after that.

Open the free plan →

Check that it stuck

Answers shown — in the app these are asked before you see them, and the ones you get wrong come back after a week.

Why is a daily loss limit needed if per-trade risk is already controlled?

Per-trade risk says nothing about the sequence of trades in a bad session — Six correctly sized losses still add up. The limit constrains the day, which is the unit where tilt does its damage.

What makes a daily limit actually work?

Deciding it in advance and treating it as mechanical — A limit evaluated in the moment is evaluated by exactly the state it exists to control.

What does a trade-count cap catch that a loss limit does not?

The day where you overtrade heavily but finish roughly flat — A flat day of eleven trades passes every loss limit and is still a behaviour worth stopping.

← The stop belongs to the idea Prop accounts: someone else’s rules, the same arithmetic →