Choosing a unit size

One to two per cent of bankroll per bet is the conventional range. The reason is survival: at one per cent, twenty consecutive losses cost a fifth of the pot and leave the process intact.

Bankroll growth is multiplicative, so a large loss requires a disproportionately large gain to recover. Small stakes keep every individual result inside the range where recovery is arithmetic rather than heroic.

A larger edge justifies a larger stake in theory — that is what Kelly describes — but only in proportion to how confident you are in the edge estimate, and most estimates do not survive scrutiny.

And that is the trap. Anything above roughly five per cent makes an ordinary losing run existential regardless of how good the picks are, and ordinary losing runs are guaranteed.

What to do with it. Pick one or two per cent, write it in currency rather than percentage, and revisit it on a schedule instead of after results.