Even as I closed my positions, I was confident it wouldn't last - but I was not 100% confident, and had already screwed up getting to that point. With appropriately small positions, I would have just waited it out.
When I originally sold a GME call (a short call position), nobody here thought that would end well. Ironically, that's the +31% profit. During the weekend when GME was nationwide news, I was confident every hedge fund and institutional investor would know about it by Monday. I predicted that GME stock would try to rise Monday, and get hit back down by selling - which is what I saw when I watched the markets that day. So I acted, and $850 strike calls with an appropriate position size. I limited my risk with "stop loss orders" to close my position if I was wrong. And then I dropped the discipline.
Later I assumed institutional investors were permanently watching GME stock, and would respond to any short squeeze with selling. But I can't point to any evidence in the stock market - unlike my earlier disciplined approach. I just thought selling GME calls was free money, backed by instituional selling. But the biggest mistake would definitely be position sizing.
That was spoiled by the second short squeeze in GME, where the price never even reached $400/share, let alone my $800 strike price. But the volatility make these $800 calls go up 10x in price, which convinced me to close positions at huge losses. If I had appropriately sized my earlier position, I could have done it again in the second short squeeze. That's the other problem: my large position meant I was taking losses during anoter opportunity to short a small position in GME calls and wait.