Hang in there

The abridged version: I got conned into being a bookkeeper instead of a student optician at my job. I'm lousy at it. I've been lousy at it for 10 weeks now. I've been miserable for 5 weeks. I considered quitting, but decided to suck it up instead.
Then I got yelled at by my boss today. Over the phone, while I was at home. I deserved it, for doing such a shit job, but the point is that this wasn't supposed to be my job to begin with.
Tomorrow, I will offer my boss two options: I'll accept a pay cut in exchange for being just being a student optician, or I quit. It's not a threat or anything; he won't lose out on much if I walk. But it'll offer me more peace of mind. It'll be a huge pain in the ass to have to start looking for a job in the middle of summer if I quit, but it's really difficult to describe just how miserable I've been these past few weeks. Anything has to be better than this.