About a year ago I resigned from a ~9-year job due to burn out (relationship issues and the death of my father were major contributing factors). I had put the decision off for a long time because I thought I should have a concrete plan first, but ultimately decided I'd never have the energy to plan next steps until I'd taken a long time off to recuperate.
So I just left. The time off hasn't fixed everything, but it has been enormously beneficial to me and I'm much more excited and optimistic about the future. I don't know how the gap will affect my career but at least now I feel like I have the energy to deal with whatever obstacles I encounter.
I was very privileged to be able to do that and I know your situation may differ; I don't have practical advice on dealing with financial concerns. But make sure you're sharing your feelings and getting advice from people around you, and - if you can keep your needs met - don't stay in an unbearable situation just from fear that something as good or better won't come along in the future.