"* Fear of failure is a great motivator. When you quit without having another opportunity already lined up, you have a lot of obvious motivation to find a new job since your income is $0. I've found it easier than lulling myself into complacency by continuing to get my income from the source I hate"

Just remember that you are a more desired candidate if you are actively employed, and that other available jobs might be just as bad or worse than your current one. Also, if you don't absolutely loathe your job, you can use job offers as leverage in your current role.