When I had been on a stressful job for 12 years and in a stressful marriage for 13 years, my sister convinced me it was time for a change.  Fortunately, she insisted on it.  She knew my situation was killing me, slowly but surely.  At first it was difficult, yes, very difficult.  My spouse went through all kinds of gyrations to get out of acknowledging he was part of the problem.  But I filed for a divorce anyway, with my parents' help and family's support.  Things didn't get better right away, I admit.  I was left with no car, a mortage, and a severely scarred psyche.  But 2 yrs after the divorce I quit the job and eventually found a job I loved, got rid of the house, moved in with my parents, and set about healing.  Yes, I did have to live with my parents for a few years (not an especially wonderful situation but much better than staying in my marriage).  But now, I am independent and loving it.  I am still seeing a psychiatrist and therapist and taking medications (since 1995.)  But I am more than keeping my head above water.  I am thriving.  And yes, the scars are still there but I see them as marks of courage and fortitude.  Onward and upward!  If you definitely get the feeling you would be happier changing your life, there is no time like the present.  Don't expect immediate relief (although there will certainly be a measure of that) but know you are doing what will make you happier in the long run.