My biggest mistak was to fully verify myself at Bitstamp, where my mistake isn't specifically targeted at Bitstamp, but just the general fact that people I don't know have access to very precious personal information. I sent Bitstamp an email a while ago, asking whether or not it was possible to have all my details be erased from their system, including my account, but the answer was that they were legally not allowed to do so. In other words, my personal information is stored on their servers for ever, and I am now forced to pay tax because there is no way to move around it. I promised myself to never ever make the same mistake again, and I will stick to that.