Nervous day at work

Today at work I was troubleshooting a clients device and I messed up something making the client get charged for something he shouldn’t have and I got reprimanded.

I’m still new with the company but I apologized and my mentor just kept hounding me to make sure I read/follow instructions more clear.

I’m new but I don’t want to be let go from messing up but it’s bound to happen when you first start anything new. He said this isn’t fire worthy but I need to follow instructions better next time. I’m anxious to go into work tomorrow I don’t want my anxiety of today to carry on tomorrow.

Any advice on how to not fester up my anxiety and feelings, and just learn and move on?