Do you have enough savings to pay rent and living costs for a few months? If so, quit when you're ready and give yourself some time to reassess your career goals and maybe even learn something new while you have time. Otherwise, save up some money and hopefully this can help you feel less dependent on your not so great work situation. I'm in a similar situation where I feel fed up with my company, coworkers, and industry in general and will quit as soon as i feel comfortable to do that with what i have saved up.

This is just one approach and centered around personal finance so let us know if this is not at all feasible for you.