One easy thing I think would help you, from what you've said, is to read a book about CBT (Cognitive Behavioral Therapy). You said you don't want to go to a doctor and you wouldn't have to for this and it's aimed at correcting that "mental churning" you mentioned. The reason CBT is so wildly popular is because you can do it on your own, without a therapist, if you want to.
The books/workbooks I've used basically help you become aware of and correct common thinking errors/unhelpful mental filters.
For a few examples, ruminating on things that are out of your control (general "you" there), catastrophizing, worrying about things that haven't and may not happen, assuming motives behind people's actions that may not be there (and not realizing it) and so on.
I even became aware of things that were just kind of in my stream of consciousness but that I wasn't especially aware of. Sometimes I'd just feel vaguely bad but not connect it to the thoughts and feelings behind it. Now it connects more easily and I'm able to think through it and stop the unhelpful thoughts.
My husband and I have worked our way through two different CBT books together. (It's nice to have a refresher course now and then). We'd read a chapter/lesson out loud every night or two, then discuss it. So it might be an activity to share with grumpy husband and help him out too, if he'd go for it. Good luck and happy soon-to-be retirement. 
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