Your reaction, training?

Hello,

How do you react and behave the next day when your trainer tells you that you're doing a poor job and aren't good enough? Not a single positive thing. It's a bit of a slap in the face if you've previously said that you're okay at work. There are positive and negative things.
If you give reasons why it was like that, it doesn't matter, it's your own fault.
Does that demotivate you?
Shouldn't the trainer motivate you?

I mean, if I'm so shitty, why doesn't he just fire me? I'm still on probation.

I'm even more fed up with it now. There are other reasons, but I'm so shitty, so if I make a mistake or something else bothers me, I should just tell you straight away? And not just say, "Yeah, you're a shitty job, but nobody tells me what I'm doing wrong."