Anxious regarding my dining class and it's driving me crazy

I go to culinary school every Thursday I go to a dining class where I do different things which include waitressing for students who eat there, for the one or two people who eat at the bristo.  I have student managers who try to help us out and make sure everything is going smoothly and teach us everything we need to know and how to operate a restaurant. 

Today, I was a waitress (I was already nervous about doing this). I haven't really done a lot of waitressing, so the student managers assured me that I got it. Before my first table was supposed to arrive, my student manager went over the steps of service with me (I got almost everything right but one singular thing). Everything was going great until I made the mistake of taking the dinner guest's bread away, assuming they were done and didn't want to clutter the table when their main meal was already there. Well my student manager noticed and gave me a frustrated look and told me to ask them if they were done with the bread before taking it away. I know I made a mistake but it made me feel incompetent, and talking about me when I'm right there doesn't help, I have a knife skills test on Wednesday so I'm anxious about that, thankfully, it's my birthday on Monday and my friends are coming over Saturday, and my family is coming over Sunday so I can distract myself.

What can I do to make me feel less anxious? I have so much that I'm thinking about and it feels like I'm slow and can't do anything. I really am scared to deal with the special event happening on Thursday for my class I'm worried about fucking it up.