Today’s topic: Why you can’t over-allocate when trading?

Let’s work out an account with you and you’ll understand.
Assume three traders, A, B, and C, each starting with $1 million, with a win rate of 50% and a risk/reward of 2:1.
Trader A (full position): full capital per trade, stop-loss at 20%.
Trader B (heavy position): use 50% of total capital per trade, stop-loss at 20%.
Trader C (light position): use 20% of total capital per trade, stop-loss at 20%.
Below, we compare them from three angles: probability, risk/reward, and black swan events.
Survival rate after consecutive losses (probability angle)
In any trading system, having three losing trades in a row is normal, so we’ll calculate based on three consecutive losses.
Full position A: each time it loses 20% of total capital. First loss: $1 million → $800k. Second: $800k → $640k. Third: $640k → $512k. After three trades down 50%, you need to win 95% to break even.
Half position B: each time it loses 10% of total capital. Three times down: $1 million → $729k. Down 27%, break-even requires winning 37%.
Two-tenths position C: each time it loses 4% of total capital. Three times down: $1 million → $885k. Down 11.5%, break-even only needs a 13% gain.
Conclusion:
After three consecutive losses, A is already in ICU, B is severely injured, and C is just scraped.
Can the system profit be realized (risk/reward angle)
Let’s keep the numbers: principal $1 million, 50% win rate, 2:1 risk/reward, trading 10 times—lose 5 times first, then win 5 times.
1. Full position A (lose 20% each time, win 40%)
Lose 5 in a row: $1 million × (0.80)^5 ≈ $800k
The account gets slashed to half and slashed again—loss up to 67%.
From $800k, win 5 times, 40% each time: $640k × (1.40)^5 ≈ $640k.
Final total profit: 76.2%.
2. Heavy position B (lose 10% each time, win 20%)
Lose 5 in a row: $1 million × (0.90)^5 ≈ $512k
Serious damage at the start—loss over 40%.
From $729k, win 5 times, 20% each time: $885k × (1.20)^5 ≈ $327.68k.
Final total profit: 46.9%.
3. Light position C (lose 4% each time, win 8%)
Lose 5 in a row: $1 million × (0.96)^5 ≈ $327.68k.
Light initial injury—loss only 18.4%.
From $327.68k, win 5 times, 8% each time: $1.76M × (1.08)^5 ≈ $590.49k.
Final total profit: 19.8%.
Conclusion:
Full position A, from down 67% to up 76%, seems like a miracle.
But if you’re full position A, your account drops from $1 million to just $320k—would you still trust your system? Could you stay calm and execute the next 5 trades that could turn things around? If you hesitate even a little, then that 76% profit has nothing to do with you.
And for light position C, although he also goes through the same 5 straight losses, he can execute each of the following trades calmly, because his losses aren’t enough to break his mindset.
Headshot angle (black swan events)
A, B, and C all buy the same stock. Suddenly, it’s filed for investigation, and the price hits an unlimited daily limit down. This trade loses 90% of the invested capital.
Full position A: $1 million all in. Loses $900k, leaving $100k. Out of the game—game over.
Half position B: $500k in. Loses $450k, account left $550k. Down nearly half—severely injured.
Two-tenths position C: $200k in. Loses $180k, account left $820k. Down 18%—just one normal pullback; a few days later, he’s back as a hero.
Conclusion:
Same black swan event—A gets headshot, B gets maimed, C only gets a scratch. It’s not because C is lucky; it’s because C never bet his entire net worth on a single trade.
Finally, a simple summary:
A full-position person is fundamentally betting that they won’t experience consecutive losses and won’t hit any black swan. But the market treats all resistance the same—you’ll find your luck isn’t as good as you thought.
A light-position person isn’t not chasing returns; it’s that he knows as long as the principal is still there, opportunities will always remain. Once the principal is gone, everything is gone.
I believe that as retail traders, before figuring out how to make money fast, you should first figure out how to die slowly. And what determines life or death is position sizing.
To wrap up, here’s one more lesson I’ve recently realized: In a bear market, trade for arbitrage; in a bull market, trade for trends. A sure win!