Risk controls for a trading system
The rules that keep a system alive long enough for a good edge to pay off — and the discipline of leaving those rules alone once the heat is on.
Risk control is the unglamorous half of a system and the half that decides whether you are still trading next year. None of it is complicated; all of it is easy to override in the moment, which is exactly why it must be coded into the system rather than improvised at the screen.
Cap the loss on any one trade
Decide in advance the small, fixed slice of the account a single trade may risk, and size every position to honour it. A system that risks the same modest amount each time can outlast a long losing streak; one that bets big on its favourites cannot — and the trade that feels best is exactly the one a relaxed cap will hurt you on.
Set a drawdown limit you will actually obey
Name the peak-to-trough loss at which the system halts and you review rather than push harder. The drawdown figure is the only number that tells you whether the returns were survivable; quoting returns without it is hiding the risk in plain sight. The word that matters is “actually”: a limit you will override the moment it bites is not a limit, it is a wish.
Leave the rules alone under pressure
The deadliest risk control failure is editing the system mid-trade — widening a stop, postponing a target, sizing up to win a loss back. A coded system protects you only if you let it run; the moment you override it by feel, you are back to discretion and the record stops meaning anything.
Let conviction guide weight within the cap
If your system grades its calls — as the codified model here does, A through D — you can lean a little harder on the strongest setups and lighter on the weakest while staying under your per-trade cap. Grading does not loosen the cap; it tells you where to put your weight inside it.
Why a small cap survives a long losing streak
The reason the per-trade cap has to be small is not caution for its own sake — it is arithmetic. Losing streaks are longer than intuition expects, even for a sound edge, and the cap is what decides whether one survives them. The figures below are an illustrative example, not a recommendation, but the relationship they show is exact.
At a 3% per-trade cap, the same 8 losers cost about 22% — and now you need a 28% gain just to get back to even.
At a 6% cap, 8 losers is roughly 39% gone, and recovery needs a 64% gain — the hole digs faster than the edge can climb out.
Same edge, same streak, three outcomes — from a routine dip to a near-fatal one — decided entirely by the cap. The small cap is not timid; it is what keeps a good edge alive long enough to pay, because the loss you can recover from is the only loss that matters.
How a conviction grade steers weight inside the cap
None of this means every trade gets the same weight. A graded system lets you concentrate the fixed cap on the calls the rules rate highest — the grade is calibrated per model, so the same letter means the same thing across very different clocks:
| Model | Grade-A bar (per trade) |
|---|---|
| Day Trade opened and closed inside one session | 0.70% avg / trade |
| Multi Hour carried from part of a session up to two sessions | 4.50% avg / trade |
| Swing Trade held for roughly 7 to 28 days | 6.00% avg / trade |
| Investing kept on a long horizon | long-horizon |
The grade is also a sizing instruction. Inside one fixed per-trade risk cap, an A call earns the full slice, a B a touch less, a C or D a fraction — because the rules have measured which setups sit where in the distribution. The grade never loosens the cap; it tells you where, within it, to put your weight. There is no E grade — it was retired so the four-step scale keeps its meaning.
What a bad version looks like
Risk control fails quietly. Nothing dramatic happens on the trade that breaks the rule — the damage shows up two months later, in a hole the edge cannot climb out of.
- A cap you relax for “sure things.” The exception you make for your highest-conviction trade is the exact mechanism by which one loss does outsized damage. Markets do not honour your certainty.
- A drawdown limit you move down. Sliding the “I'll stop and review” line lower each time it is hit, so you never actually stop. The limit only works if it is fixed before the pain arrives.
- Revenge sizing. Doubling up to win back a loss fast. It converts a controlled drawdown into an uncontrolled one on the worst possible day to be wrong.
- Risk measured in lots, not money. Thinking in “3 contracts” rather than “£135 at risk.” Until risk is in money against a stop distance, you do not know what any position can actually cost you.
Each is the same error: treating a rule written in calm as optional once it costs something. The whole value of coding the rule is that it does not negotiate when you would.