I need to quit a seasonal job at a large big box hardware store because of many reasons, one of which is back pain. This job often has me lifting heavy objects. Either through poor form or haplessness I recently hurt my back.
A personal friend of mine, also an M.D., examined me and determined some issues to confirm my suspicions. He told me more stress on my back could lead to chronic issues. This seasonal job offers no personal time off and expects weekends to be always covered, so I doubt waiting for recovery would be an option.
I know I should have other work lined up before leaving, and this job itself was just a stopgap until I decide on an official place to relocate.
How do I immediately send a letter/email of resignation to HR or whatever would be the best method of quitting this job immediately before I aggravate my back more at work? I do not want this biting me in the "back" (pun intended).