Personally I am new to the job as well (although I have come from an engineering background).
The main reason for ACS is to see if you are safe.
The fact that you failed must mean you was deemed unsafe?
I did my first Assessment 11 years ago and even though I have 2 engineering degrees I still learn things daily.
I can honestly say if I look back now at what sort of an engineer I was then (just after my ACS), I was rubbish and totally clueless.
The Assessment really is just the start and I have learnt so much since.
Experience is everything.
Look upon passing as the start and not that you are miraculously as good as any engineer out there.
Dont get me wrong, just because someone has been in the job 30 years does not make them a good engineer (I have met many that are not) but the ACS is just the license to start learning.