The biggest single mistake was buying Tepnel Life Sciences, who were (I was convinced) just about to reveal something truly marvellous (which I can’t remember now) so that their share price would go straight up.
The worst strategy I ever used was to keep buying blue chip shares as all the major stock markets fell.
The worst tendency I suffer from is to become over-confident and throw risk management out the window.
Hey ho. I think I’m over these things now.