I did this once. I knew it was time to quit when I started crying as I drove home Friday night knowing I would have to come back on Monday.
I went home, revised my resume, wrote my resignation letter and turned in my two weeks notice first thing Monday. At the time I was single, with no other income and no savings to speak of.
I realized that no matter what I had to give up or do it couldn’t be any worse than the way I was feeling every day. The weight that was lifted when I turned in my notice was the motivation I needed to get moving on finding another job.
I called and emailed everyone in my professional network and started looking through the phone book for organizations where I thought I might want to work and used my lunch times to call them. One of the organizations I called just happened to be hiring for a job in my field (which by the way I had never seen advertised anywhere).
I applied, got the job and it started exactly one month to the day after giving my notice. If it weren’t for the fact that I paid attention to how I really felt, had the faith in my abilities (which had gotten me the dreaded job I was leaving in the first place) and taken a leap into the great unknown I would have probably stayed until I collapsed, got fired or something worse!
No job is worth your life or your sanity! That experience taught me that living my life out of fear of the unknown is not really living at all.