Common beginner mistakes, and keeping score honestly
Every mistake in this chapter is the same mistake wearing different jerseys.
Nine chapters in, you know more theory than most people trading this weekend. So here is where beginners actually lose, and it’s rarely the theory. It’s the same mistake, over and over, in different jerseys: grading yourself on results instead of process, one game at a time.
The jerseys it wears
Results-worship.Your 70% call misses and you tear up the model; your 30% flyer hits and you’re a genius. Chapter 3 already dismantled this (a single result grades nothing), but knowing it and feeling it are different educations, and only the journal below closes the gap. The revenge trade.Down on the early games, you size up the night game to “get it back.” Chapter 8’s Tuesday-you never approved that trade; the person placing it is the one worst equipped to. The hot streak.Five straight and you feel bulletproof, right when a 55% trader’s arithmetic says a streak proves nothing and the sizing creep it inspires costs everything. Everything, everywhere.An opinion on all thirty games, because having no opinion feels like losing. Chapter 6 already gave the verdict: the pass is a position, and it’s free.
The fix is a notebook
Every jersey comes off with one habit: write it down before, grade it after, keep the misses. Before each position: the probability you believe, the price, one sentence of why. After: what happened, no edits. In a month you have what memory will never give you, an honest sample. Bucket it like chapter 4 taught: are your 70s real 70s? Is the long end of your own board leaking, chapter-5 style? You are running calibration on yourself, which is the whole reason the habit works.
Memory is a highlight reel. A journal is a track record. Trust the one that can’t edit itself.
This is, not coincidentally, how our own desk operates. Every number published before the event, graded in public after, misses kept up with a red mark. Not as a flex: as the only known cure for the disease this chapter describes. A desk that could delete its misses would, eventually. So we built one that can’t.
The quiet part, in full
These markets are entertainment with arithmetic, and this book’s only promises are about honesty, not outcomes. So, plainly: trade only money you have already written off. If it stops feeling like entertainment (chasing to get even, hiding the scale of it, trading money that matters), stop, and talk to someone. The National Council on Problem Gambling’s helpline is 1-800-GAMBLER, and our responsible-play page lists more resources. Under 18 (21 in many US states), none of this is for you yet. The market will still be there.
That’s the book. Read prices as probabilities, name your number first, demand calibration from anyone selling you certainty (including us), size like someone planning to be here next season, and keep a record that can’t flatter you. It’s not a system for beating anything. It’s the equipment for not being beaten by yourself. Welcome to Saturday.
Frequently asked questions
- What is the most common mistake beginners make in prediction markets?
- Grading decisions by single results: celebrating a bad trade that got lucky, abandoning a sound process after one loss. A 70% call that misses was still, most of the time, a fine decision; a 30% call that hits was still, most of the time, a donation that got refunded. Process grades over many results; one Saturday grades nothing.
- How should I track my prediction market results?
- Write every position down before the outcome: the probability you believed, the price you traded, one line of reasoning. Grade everything after, keep the misses, and bucket your stated probabilities exactly like chapter 4's calibration check. A month of honest entries teaches more than a year of remembered ones. Memory is the most creative editor there is.
- How do I know if sports trading is becoming a problem?
- Honest tells: trading money whose loss would matter, chasing losses to get even, hiding activity or its scale, and it no longer feeling like entertainment. If any of those ring true, stop and talk to someone. The National Council on Problem Gambling's helpline is 1-800-GAMBLER. Under 18 (21 in many US states), none of this is for you at all.
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Already on the list? Download the PDF. And as everywhere on Maiden: these are probabilities and mechanics, graded in public. Nothing here is betting advice.