Over Estimating One's Ability.

This seems like a typical my-thing. I've fallen into this trap many times. It looks people in my profession fall prey to this too.

That’s one reason I don’t miss IT, because programmers are very unlikable people… In aviation, for example, people who greatly overestimate their level of skill are all dead. - Philip Greenspun, co-founder of ArsDigita, excerpted from Founders at Work.