GaryJon,
Good luck with your training! It's a great job, most of the time.
If I may offer a bit of advice, quickly learn not to take pax complaints personally. A bit of empathy goes a long way. Flying these days just isn't as fun as it used to be, either for pax or crew.
We have little control over most things, except for our attitudes. All you can do is apologise and offer a comment card to send to Consumer Affairs. Your CSD might be able to drop a note to catering or Inflight Dining and Cabin Services.
Many times, the pax just want to vent a little.
Best wishes to you on your new career!
Dea