sorry im a bit late on this one but i have had a similar experience.Could you go part time in your job and start a business or get another job? I wouldn't pack your job in before you have another one lined up,i did it, big mistake, i did it because i thought packing the job in would make me clearer,it created a new set of problems.I remember physical workers saying that when they hit late 50's work became harder,some do work into a grand old age ,but most don't.
Im nearly 67 and eat well ,exercise etc but i get soooo tired after manual work. I'm a big fan nowadays of kindness towards myself,took me 60 odd years to get to that one!
good luck with your decision
What were the first ever records that you bought and when?
Parents-in-Law. What do/did you call them?