I think the Dunning-Kruger effect would be the best explanation of what many of the amateur investors I meet (including myself) do in these markets, to a different degree of severity. It is a real effort to keep tabs on your own biases. From personal experience, it is like splashing cold water in my face at every step I take even if I am damn sure I don't need it. To be honest, 9 out of 10 times it turns out I do.