Beyond vitamin d3 + k2, you just have to tough it out.
It's your mind fucking with you.
This is a positive about having a big family (kids, grandkids etc). When you get older, you don't sink in your own thoughts too much.
You ever thought of just selling up the house/renting it out and living nomadically in 3rd world beauty spots? Rural life can bring you peace sometimes. Without kids, there's nothing really restricting you from getting out of this shithole.