I can relate. I quit a cashier job after only like three weeks because I kept making mistakes, I had basically ZERO training and they threw me on the cash register as if I was somehow automatically supposed to know everything. I worked with all females, and they would look at me like I was an idiot. Definitely felt like bullying a couple of times. They were all older than me and were on the job much longer than me, but they kept making me do everything and sort of felt like they were throwing me the "hot potato" when it came to all the difficult work just because I was new there. Hated it, and that was my very first job too, so it made me scared to get another job because I figured every work place was probably like that.
Making mistakes at a job happens pretty often I would assume, if you're pretty new. It just goes to show you the lack of training they gave you, which is their fault. If you aren't totally confident in what you're doing, the training wasn't good enough.