Job too good to quit & too good to stay! to quit a very stressful job for health, marriage, kids, etc.?

job 18 years, doing the job of at least 2 people, not a hard job--just a very stressful job! I start getting mentally & physically sick on Sunday just dreading Monday mornings! I cant seem to even enjoy the weekends knowing how short they are! My house stays a wreck, I have stopped cooking, I am tired or screaming all the time, etc. I make good money & in fact, I am the primary bread winner. I am also on 2 antidepressants and 2 BP meds! We are not a materialistic family. Our biggest expense is private school for our twin boys (10 years old). I do think that with very statigic planning that we my be able to continue with private school. I dont expect staying at home to be a 'walk in the park'. In fact, I expect it to be harder but way more rewarding and hopefully more enjoyable. I dont want to exchange one set of worries for another though. Anyone with similiar experiences? any words of wisdom? Thanks for any input! :)