Training is a long, hard and relentless but being a well-rounded and motivated individual will stand you in good stead - not enough on it's own to get you through the training but a good start.
I don't mean to make it sound like a real downer because it's not. You'll hopefully enjoy the group camaraderie and form lifelong friendships. Just that it
is tough. Maybe I'd better not mention the historic pass rate........
FWIW there are signs that the current selection process is doing a good job.