Jag, don't believe everything you hear. They can say all this officer first bull as much as they want, but at the end of the day people get chopped for inability to fly, not inability to drive a ship or manage a division.
Orca, the whole point of aptitudes is to find your aptitude, not your effort level. The clue is in the name.
I am truly catastrophic at maths, but it didn't seem to be a problem.