I used to be a teacher, until I found out I had no class.
I used to be a doctor, but I didn't have the patients.
I used to be a barber, but I just couldn't cut it.
I tried to be a tailor, but I just wasn't suited for the job.
I used to be a math teacher, but I had too many problems.
I used to work in an orange juice factory. They said I couldn't concentrate, and I got canned.