Have you considered therapy? You have experienced a big change in your life. Having someone to talk about those changes with may help you process the changes. While I haven't retired either, in the last few years there have been changes at my job which has basically made me "lower the bar" as as far as how I view responsibility. Not my circus, not my monkeys is a hard adjustment to make.
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"It is the unknown around the corner that turns my wheels." -- Heinz Stücke