I've worked at three airlines in my career. And I find if you come in well prepared and a positive attitude, they'll work with you.
Know your flows, profiles, call outs, memory items and limitations and that's 90% of the battle.
If you show enthusiasm and willingness to learn and not talk back to the instructor, I find instructors will bend over backwards and do whatever they can to get a trainee through
(Been there done that)