I don't intend this post to be sexist in any way so i'm sorry in advance if i offend anyone.

From a young age most boys are told not to hit girls. A few years ago at my first competition i was fighting a girl a belt above me (purple) who was slightly taller and a bit older but had a lot poorer technique than me: weak blocks, slouching stance, slow punches etc (all the schools involved were a bit mcdojo-y) but i found i had an in built problem fighting this girl and fought only defensively never landing any blows. i couldn't bring myself to hit her from the saying that had been pounded into me for years. has anyone else had this problem?

(and if it wasn't for her i would have been silver not joint bronze lol grrr )
Go seek the advise of a qualified instructor.