I don't know why I don't act in my own best interest though. It wouldn't surprise me if there was some societal element to it, but it really seems strange/weak/victim-ish to blame something external for what really does feel like a personal shortcoming - after all my own sister doesn't seem to have the same sort of "conditioning".
Are there tips out there to help getting over the fear of negotiating? Not really thinking about looking for something else at the moment, but there always seems to be a "next job" out there somewhere.