What's the worst mistake you did with your Bitcoin? It can vary from starting to use Bitcoin to buying dumped Altcoin to gambling.
The worst mistake I did is I didn't care when firstly hear and read about bitcoin in 2011. Half part of me just deny it and think that it's just like scam and you know something like that. That's the worst and it remains many bad things, I start when BTC flies and mooning like crazy.