Having a part-time job for the first time, quitting for the first time?

It's summer holidays before I start my last high school year. I've worked for 3 days at this restaurant and it's too hard for me to do. I work in the evening so i can't hang out with my mum now that she finally has time, I work like crazy, but I still make mistakes. My boss texted me that the next time I make a mistake I'm paying for it. All this made me quit after 3 days only. I'll tell this today to my boss, but I'll also say that I'll work today because I already said I will. Do you think that my boss will be angry? I'd love to still come to that restaurant though..