Good reasons to quit without having another job lined up

Long before I was old enough to have a job, I heard my parents say, “Never quit a job before you have another job to go to!” I heard them tell my older brothers and sisters “Wait until you find a new job... then quit!”

It’s sensible advice and we all try to follow it. Sometimes we try so hard to stick it out at a miserable job that we get sick as a result.
Sometimes we know we don’t have what it takes to get a new job right now.