You go and talk to your boss in person in private - face to face.
I'm sorry, Mr. White, but I am unable to continue to working in my current job. I've had some medical issues come up that has forced me to take a step back from working.
I appreciate all of the training that I've had. It's been a good company to work for so far, but at the present time, I must focus on my health. Thank you so much.
Shake his or her hand.
Life will always endure.
It has for thousands of years.
There is nothing humans can do to
stop it. It is here for a reason, to protect
all life everywhere. Don't worry you are on
the right track. Your being observed.
A few comments---
Taking a job and then finding out that it is not something you really like to do is still a good outcome---don't feel bad about it.
Tell your boss that you have decided precisely that---it's quite accurate.
(I would avoid mentioning health issues as a reason--- no use letting that float around out there.)
Given your status as a casual, he may just tell you to leave immediately after you indicate you no longer want to work there---that would not be unusual.
Or---he may want you to not quit and may want to ask whether there is some possible problem with the job.
Didn't find the answer you were looking for?