I understand about it being different for everybody. I knew a woman a few years back that retired from the company I work for at 70 years old. In a year she came back and said she couldn't stand doing nothing. Some of her co-workers thought that possibly what she couldn't stand was being home 24/7 with her husband, who was already retired. I got a laugh out of that, but who knows.
I have never been one that thought I would have nothing to do if I wasn't working. I know plenty to do on my own and if not, I have friends that go places as a seniors group and they have a lot of fun, so to me, there are plenty of things I'd love to do if I weren't working. I cannot even imagine being bored for a minute !
It is very true, there is no valid use in holding onto things that can't be changed.
I've heard similar stories and have been warned about it, but only by peopp who don't know me well; those who do know what's up. Like you, there'd be plenty to do.