Lesson Learned: Over-leveraging on 'Will SPX close above X' Kalshi contracts

Was feeling pretty good about my read on a couple of short-term SPX directionals on Kalshi a few months back. I'd had a decent run on some $GOOGL and $TSLA earnings contracts prior, which probably inflated my confidence a bit. Saw a few 'Will SPX close above X' contracts with good probabilities, or so I thought. Instead of sticking to my usual sizing, I went in a bit heavy, especially on the ones expiring same-day. The logic was sound: short-term bounces often happen after morning dips. Problem was, my entry wasn't precise enough, and the market decided to grind sideways/down just enough to keep me out of the money. Ended up rolling some, which just dug a deeper hole.

The core mistake wasn't the read itself, but the sizing. I traded it like a certainty, not a probability, especially for same-day expiries where the gamma risk is intense. Lost a decent chunk that day, enough to reset my ego. The lesson, always, is to stick to your risk parameters, especially on these binary outcomes. It's easy to get sucked into thinking you have an 'edge' on something that's essentially a coin flip with good research, but that edge evaporates with improper sizing. Treating Kalshi contracts like options without the volatility crush decay (just time decay to settlement) means your 'theta' is really just the probability shift. Don't overpay for that shift.