How do you go about quitting a job? How do you go about quitting a job you like?

I didn't so much quit today as let my boss know that I can't do certain aspects of my job (inb4 Jiro's a prostitute) but it was really hard to put on the table 'cause I didn't want to disappoint. Also because this lady is new to the position and so I don't actually have rapport with her yet.

I've never actually quit or been fired from jobs I've had. I just sort of... stopped going. Or stopped being given work. It's like, the no frills way to do things. I like it!