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Position size after a streak: the trap of scaling with emotion

After wins, the temptation to increase size grows. After losses, it shrinks or, worse, jumps up for revenge. In both cases, size reflects feeling rather than a rule.

Consistent sizing is crucial for reading the statistics. If size varies randomly, a few large trades dominate the results, and the outcome depends more on when the large trades happened than on edge.

A fixed fractional approach, where size is a set percentage of the account, adjusts automatically as the balance changes, avoiding emotional decisions. The percentage should be small enough that a long losing streak is survivable.

Some traders scale with volatility, reducing size when the stop distance is wider. This keeps risk per trade roughly constant.

If increasing size after wins is part of the plan, it should follow a formula decided in advance, with a cap.

The question is not whether to scale, but whether the scaling follows a rule or a mood.

How is trade size determined, and has an emotional size change ever damaged a good week?

My worst week in two years started with a good one. I had four winners in a row, bumped my lot size by about half because I felt sharp, and then a normal losing stretch of three trades cost more than the previous four had made. The edge hadn't changed at all, only the size had.

What fixed it for me was a fixed fractional rule written on a sticky note next to the monitor: 0.75 percent of the balance per trade, recalculated once each morning rather than after every trade. That removed the in-the-moment decision completely. I also added a hard cap so that the size could never be more than twice my starting size, even after a great month.

For volatility I only scale down, never up. If the stop on the chart is wider than my usual, the lot size shrinks to keep the dollar risk the same. Since I started tracking it, my equity curve is a lot smoother and a bad day no longer ruins the week.