Ok, so I come from a bit of a different place and this is what I've learnt: Feelings are not always fun, but they will not kill me. I don't like feeling scared, I don't like feeling like a burden, I don't like feeling like I'm not up to speed. However, if I possess the basics to keep a person safe and protect my license, I can make it through, one day at a time. Stay in the moment... when you are in that moment, ask yourself, "what is so bad about this moment?" If it's feeling scared, or tired, or hopeless, ask yourself if it's going to kill you? If it isn't going to kill you, you're safe. One foot in front of the other... Make it through a task, breathe. Make it through the next task, breathe again. Break your days down into as manageable blocks of time as you need to.
The preceptor: Is she going to kill you? She can't, she'd lose her job. In our local hospitals, preceptors get paid for precepting. I'm not sure how it is in your hospital. If she's getting preceptor pay, she is there to teach you. If she's not, she still agreed to be your preceptor. You have the right to ask questions when you are uncertain or for whatever...
This may all sound really silly, but I ask myself all the time if something is going to kill me when I get all spun out about it. And I feel stronger when I make it to the other side and don't die!
If it is still too much, have a sit down with your boss and just be honest. She can't kill you either! Wooooooooooooo