You've done no such thing. Apology not necessary. What is this thread for, after all, but to air grievances and talk with people about them?
I think all that's happened is you brought up an issue (bad trainers) that people feel passionately about, myself included. If you felt anger in some of the responses, be assured it wasn't towards you but rather your coworker/trainer.
We all slip at times, and starting a new job is stressful. One thing I might recommend is instead of focusing on "not letting it show", give yourself a place/time where you can let it all show through for a bit without judgement. Having a trusted friend who you can do this with (or even just coming on this thread and venting occasionally) can be a huge help, and can sometimes help you keep your depression from interfering with other parts of your life.Work is going a little bit better, though I still feel... a little cheated. I worked pretty hard to qualify for my job but I still feel like an easily replaceable cog. So all that effort feels a little like a lateral move. It could be worse I guess. At least I'm not doing customer service anymore.
On another note, even though I've struggled with depression and anxiety nearly my entire life, I've been pretty good about not letting it show. I feel like now I'm slipping badly.