I forgot about my BTC wallets. I tracked them down years later and sold for a nice profit simply because of forgetfulness.

Hehehehe... I think that a lot of crypto millionaires became millionaires similarly... They forgot about it, and remembered on the next pump... 😃

I got into mining much later, in early 2017, with GPUs and ETH mining... If I didn't play around with altcoins and just HODL ETH, I suppose my current portfolio would be in a much better shape... 🤣