Lesson Learned: Overtrading on Polymarket and the "Certainty" Trap

Thought I'd share a recent screw-up on Polymarket, something that cost me more than it should have. It wasn't a massive amount, but the principle behind it is a classic trading mistake I thought I was past.

There was a market on a specific tech company's quarterly earnings – specifically, whether their revenue would beat estimates. The initial odds for "Yes" were fairly low, reflecting the general sentiment that the company was struggling. I did my own quick diligence, looked at some analyst revisions, and saw a few indicators that suggested a beat was more likely than the market was pricing in. So, I took a position on "Yes". The odds started to move in my favor, which was great. Instead of just letting that position ride or trimming some as it approached more reasonable odds, I got greedy. I started looking for other markets that seemed "obvious" after the fact. There was another market on a different company's new product launch success – again, sentiment was bearish, but I convinced myself I saw a clearer path to success than the market.

My mistake wasn't necessarily taking the initial informed position, but doubling down on the feeling of certainty across multiple, unrelated markets. Each market might have had a slight edge, but by betting on several at once, I compounded my exposure to potential market irrationality, or simply, my own misjudgment. The first earnings market resolved as a beat, which validated my initial read. But the second market on the product launch went sideways, then down, eventually resolving unfavorably. My small win on the first was wiped out and then some by the overconfidence and overtrading on the second. It's a reminder that even when you think you've got an edge, it's easy to get sucked into the idea that every low-odds market is an opportunity. Discipline in sizing and managing the number of active positions is key, especially when dealing with these more speculative prediction markets. You might be right often, but you only need to be wrong big once.