I'm convinced that most people who think they are bad at math only think that because math is typically taught in a way that makes it seem tedious and useless.
Mind you, I also think there are differences in natural aptitude and the degree to wich on connects with the subject. Speaking for myself, I mostly did well through high school math--geometry proofs less so--but mostly just got by on the more advanced math I needed for an engineering degree.
(Then I tutored a group of students in business school who basically handle high school level algebra.)