A SPY 0DTE averaging-down mistake that cost me $1,514

Old trade, but still one of the clearest lessons I’ve had from trading 0DTE options.  I’m sharing it because the chart and P&L explain the mistake better than I can.  I had a bullish read on SPY and bought 737 calls at the 9/21 EMA. This was a 0DTE trade with an initial position of around 10 contracts.  The setup looked all right going in and I kept my invalidation level at 733.  SPY started dropping. Instead of exiting at 733, I told myself it would bounce from the 50 EMA. I added roughly 7 more contracts to lower my cost basis. SPY continued dropping. I avg down again, and ended up with a bloated position in a trade that was already showing me the original idea was wrong from the first red candle. Look at the chart. That big drop after entry wasn’t just a small dip. It was SPY breaking the level I had planned to use as my exit. That 50 EMA didn't hold. Position just kept bleeding. For transparency, this trade was taken in Vanquish evaluation account. It became a useful lesson in how quickly ignoring one stop can affect the rest of a trading session.  **The P&L tells the rest:** \-$445.50 - That's where the original exit should've been. Small loss, manageable. Then -$1,514.80 - The loss after ignoring the original stop and averaging down twice. Same day. Same thesis. Just more contracts attached to a losing idea each time. **Why averaging down felt logical** 10 contracts at entry. SPY drops. Add seven more at a cheaper premium. The cost basis goes down, so it feels like the trade needs a smaller recovery to break even.  I went from 10 contracts to roughly 17 contracts on a 0DTE SPY call with theta running every minute. Cost basis is lower but total risk is almost double the original. And SPY needs to move significantly back in the right direction before expiry which is today to make any of it work. **What the 733 stop was supposed to do** 733 was the line where the trade was wrong.  I didn't honor it. SPY broke 733 and instead of closing I added. Turned a pre-planned small loss into a session that genuinely hurt the eval. My rule is simple now, the original position size is the maximum position size.  If I enter with 10 contracts, I don’t turn it into 17 because the premium is cheaper. If my strategy is invalidated, I exit.  No adding. No “one more entry”. No lowering the cost basis after the setup has failed.  With 0DTE, there is very little time to recover from a mistake. The clock is running from the moment you enter. Every wrong decision costs more than it would on any other instrument. \-$445 was the lesson. -$1,514.80 was the cost of refusing to take it. Have you ever turned a manageable loss into a much larger one by averaging down?